All the latest news and rumours from European football's winter transfer window.
Transfer talk: January 2 - Demba Ba set to kiss Newcastle goodbye
The Blues were given permission to talk to the 27-year-old Senegal international after meeting the £7 million (Dh41.7m) figure stipulated in the deal he signed with the Magpies during the summer of 2011.
Ba was withdrawn from the Newcastle squad for last night's Premier League clash with Everton at St James' Park as a result.
A club statement said: "Newcastle United can confirm that Chelsea Football Club has made an official offer for Demba Ba which has triggered the release clause in the player's contract.
"The club has given the player permission to speak to Chelsea FC and therefore he will not be included in the squad for tonight's game against Everton."
The move comes as little surprise after the Londoners held talks with the player's representatives at the weekend.
Those discussions were later described as "unproductive", but there was a feeling that it would not be the end of the matter.
Newcastle have tried unsuccessfully to renegotiate Ba's contract in recent months to prevent a repeat of the speculation which surrounded him during the summer.
However, with the former Hoffenheim and West Ham United forward's representatives actively trying to move him on - Magpies manager Alan Pardew lashed out earlier this week at the network of people purporting to be looking after the player - their hopes of securing him on a firmer footing always looked doomed.
Ba has been a major hit on Tyneside - he scored 16 goals last season and took his tally for the current campaign to 13 with a double in the 7-3 defeat at Arsenal on Saturday - and Pardew was desperate to keep him.
However, Newcastle were not prepared to shatter their wage structure to accommodate his demands.
The initial three-year contract was complicated with Newcastle looking to protect themselves after Ba had earlier failed a medical at Stoke City because of a chronic knee condition, while the player kept his options open.
He has now opted to consider the alternatives, although it remains to be seen if Chelsea are prepared to give him what he wants, with any deal sure to cost them way in excess of £7m even before his salary is taken into account.
The Magpies will receive only a proportion of the fee should the transfer go through, but have actively been pursuing a replacement, with Marseille's Loic Remy understood to be at the top of their list.
Meanwhile, the Magpies appear to have won their battle with the Nigeria Football Federation, for the time being at least, after Shola Ameobi was left out of the final squad for the African Cup of Nations.
Pardew has insisted for several weeks that the 31-year-old striker would not be joining up with his country despite warnings from coach Stephen Keshi that he would demand that Fifa take action if he did not.
Nigeria's media officer Ben Alaiya told BBC Sport: "Shola's refusal to answer calls gave Keshi no other option than to allow him to concentrate on his club.
"The coach and team secretary made several attempts to reach Shola but there was no answer. The coach waited to hear back from him but a call never came.
"A decision on the next move will be made at the appropriate time."
DANIEL STURRIDGE PACKING FOR ANFIELD
Liverpool have completed their first signing of the January transfer window by securing Chelsea forward Daniel Sturridge on a long-term deal.
The Reds have been pursuing the 23-year-old for some time, having first expressed their interest in him back in August, and are believed to have paid in the region of £12 million (Dh71.8m).
"I am humbled and happy to be here," Sturridge told liverpoolfc.com.
"Brendan Rodgers said he sees me here for a long time - and I also see myself here for a long time. I've not signed here to play for a couple of years and then move on.
"I've signed to be here for as long as possible. It's a humongous club - for me, one of the biggest in the world - and to have the fans and world-class players we have here is amazing."
Borussia Dortmund would be glad to offer Nuri Sahin a return to the club if he became available at the right price, according to the Bundesliga club's director of sport Michael Zorc.
Sahin was voted the Bundesliga's Player of the Year when Dortmund won the title in 2010/11 before he joined Real Madrid.
After failing to hold down a regular berth in the Madrid side, Sahin moved to Liverpool on a season-long loan, although he is still contracted to the Spanish club until 2017.
The Turkey international has failed to rediscover his best form and Dortmund are monitoring his progress.
"Of course we are following Nuri's career - he's one of our lads," Zorc told the Bild newspaper.
"We said to him back then [when he left], if Nuri says that he wants nothing other than to play in Dortmund, then we will deal with the issue.
"But it has got to be manageable, and nothing has changed in that regard."
Dortmund have said they would not sell attacking midfielder Mario Gotze under any conditions.
"Mario has a long-term contract with us and he feels very happy here with his family and friends in Dortmund," Zorc said.
"There is nothing that suggests that will change. He is 20 and, consequently, far from reaching the end of his development."
Wigan Athletic this morning completed the loan signing of Angelo Henriquez from Manchester United.
The move, which was expected, will see 18-year-old Chilean Henriquez join Wigan for the rest of the current season.
Henriquez was brought in by United last summer from Universidad de Chile and has already made his full international debut, with Wigan's manager, Roberto Martinez, hoping he can make a big contribution over the coming months.
Wigan are in a familiar position of battling to avoid relegation from the Premier League and lost 4-0 to United yesterday.
Martinez told Wigan's official website: "We're really excited about Angelo because he is a very young man with a huge potential; he's a goalscorer with clever movement inside the box and has had a very successful time with his former club Universidad.
"We hope to have a good partnership in terms of allowing Angelo to develop as a footballer and learn of the demands of the English game, because I feel he can bring us something different in the forward line.
"I'm sure the fans will give him a great welcome on Saturday and it will provide him with the perfect opportunity to begin his experiences on the pitch in English football which is very exciting."
Henriquez could make his Wigan debut in Saturday's FA Cup third-round home clash with League One side Bournemouth.
"This is a fantastic opportunity for me and I am really excited after the manager has given this chance for me to prove myself," the teenage striker said.
He becomes the second mid-season recruit by Wigan, who confirmed the signing of Honduran midfielder Roger Espinoza from Sporting Kansas City last month and are waiting for the Honduras international to obtain a visa.
Reading are close to signing Australia international Tom Rogic.
Playmaker Rogic, 20, has shone for the Central Coast Mariners and is due to reach the end of his contract in May.
He came close to joining Reading in 2011 when the Berkshire club failed to secure a work permit for him.
Mariners chairman Peter Turnbull told SBS' The World Game: "We have been in discussions with Reading and both clubs are fairly satisfied with what's on the table and now it's up to Tom to reach a personal agreement with Reading.
"I am not going to say what the figure is but there is an agreement there. Of course we don't want to see him go.
"I'd like to have Tommy here for another six years because he's a special player.
"But the reality is that quality Australian players will always want to test themselves overseas where they can command the salaries and exposure they cannot command here.
"You have seen it with the Harry Kewells, Brett Emertons, Lucas Neills, Jason Culinas and so many more over the years.
"We could keep Tom here until May when his contract expires but then he could leave for nothing, and we as a club would be out of pocket. It's a situation where our hands are really tied.
"The way things are now I would expect that things will be resolved by the end of the week concerning Tom and it may be that he will decide to stay, though considering his past association with Reading perhaps that would be unlikely."
Reading director of football Nick Hammond said in The Sun: "We've been monitoring Tomas closely for the past year or so and were really disappointed when we couldn't sign him because of those work-permit issues.
"Our opinion of him has only got higher.
"He's a smashing lad. I have no doubt he has the potential to play in the Premier League."
Rogic made his senior Australia debut against South Korea in November.
Reading stand 19th in the Premier League table after 21 games.
Mathieu Debuchy was expected on Tyneside today to start the process of formalising his move to Newcastle United.
The 27-year-old Lille full-back was due to travel to the north-east of England after the two clubs finally agreed a fee, understood to be in the region of £5 million (Dh29.9m), over the weekend.
However, with a medical to complete and personal terms to discuss, his transfer is unlikely to be concluded until later in the week.
Whether or not the France international is among the crowd for tonight's Barclays Premier League clash with Everton at St James' Park remains to be seen.
Debuchy has been in Newcastle's sights for some time, and manager Alan Pardew was hugely disappointed to miss out on one of his major targets after the two clubs were unable to reach agreement over him despite protracted negotiations during the summer.
However, with Danny Simpson having rejected the Magpies' latest contract offer with his current arrangement due to expire at the end of the campaign, the right-back position has become a priority.
Pardew is also keen to add a central defender to his squad with injuries and suspensions having exposed the lack of depth among the current crop, while a striker is on his wish-list regardless of Demba Ba's situation.
The manager has not given up hope of hanging on to the Senegal international despite his representatives having held, so far unproductive, talks with Chelsea, but Marseille's Loic Remy is high on his wish-list.
However, sources on Tyneside today played down a link with West Bromwich Albion frontman Peter Odemwingie.