Juan Martin del Potro faces a further lengthy injury layoff and will miss Wimbledon next month after fracturing the patella in his right knee for the second time in nine months.
The Argentine slipped on court towards the end of his first round win at Queen's Club in London over Denis Shapovalov on Wednesday and could also miss the US Open later this year.
"The medical studies done last night in a clinic in London show that Juan Martin del Potro has suffered again a fracture in the right patella," Del Potro's head of communications Jorge Viale tweeted on Thursday.
"After consultation with his doctor, Angel Cotorro, it has been determined that it will require surgery.
"This will take place in the next couple of days with a date and location to be determined."
Del Potro suffered the same injury after falling heavily in a match against Croat Borna Coric at the Shanghai Masters in October.
The world No 12 returned to action in February, but has been limited to just five tournament appearances this season and will not recover in time for Wimbledon which begins on July 1.
Del Potro's career has been ravaged by injuries, most notably to his left wrist that saw him sidelined for most of the 2014 and 2015 seasons. However, he battled back to the top of the game, reaching the Olympic final and led Argentina to the Davis Cup title in 2016.
Despite losing his first grand slam tournament final in nine years at Flushing Meadows in September to Novak Djokovic, Del Potro rose to No 3 in the world last year before being struck down again by injury.
Meanwhile, top seed Stefanos Tsitsipas avoided a slip-up at Queen's as he breezed past British No 1 Kyle Edmund 6-3, 7-5 in their rain-delayed first round match.
Tsitsipas was grateful to polish off Edmund in straight sets after resuming at 3-3 in the second set after rain on Wednesday forced the match into a second day.
The 20-year-old Greek will be back on court later on Thursday to face Frenchman Jeremy Chardy as organisers try to catch up with lost time early in the week.
Flying into R2 💨@StefTsitsipas finishes off Kyle Edmund 6-3, 7-5 to win his first ever match at @TheQueensClub.
— cinch Championships (@QueensTennis) June 20, 2019
See you again later on Centre, Stef! #QueensTennis pic.twitter.com/fzZkJJUjuj
The world No 6 also saw his chances of winning a first title on grass helped as defending champion Marin Cilic and last year's Wimbledon finalist Kevin Anderson crashed out in the second round.
Anderson, the second seed, looked understandably rusty in his first tournament appearance since March due to injury.
The veteran South African battled back from a set down to Gilles Simon, but the Frenchman prevailed 6-1, 4-6, 6-4.
Fifth-seeded Cilic - who also won the Queen's title in 2012 and reached the final on two other occasions - went down 6-4, 6-4 to 26-year-old Argentine Diego Schwartzmann, who is appearing at Queen's for the first time and recorded just his third win on the surface.
