Sir Alex Ferguson's side struggle to an unconvincing 1-0 win over AmaZulu, while Chelsea's new signings find the net in a 4-2 victory over Seattle Sounders.
Victories for Manchester Utd and Chelsea in pre-season trips
Manchester United began their preparations for the new season with an unconvincing win over mid-table South African outfit AmaZulu in Durban.
Federico Macheda scored the only goal midway through the first half as an experimental United side looked short of their best.
Goalkeeper Anders Lindegaard called on to make a couple of decent saves, while the hosts were only denied a penalty due to an offside flag.
Yet with four players in the United line-up who have yet to make their competitive debuts - and more introduced in the second half - perhaps a low-key outing was to be expected.
United new boy Shinji Kagawa made a late substitute appearance too and Ferguson will expect a substantial improvement during United's 22,000-mile pre-season campaign.
Macheda in particular will hope to continue to impress, before England forward Wayne Rooney and Danny Welbeck link up with the squad in Scandinavia next month.
Macheda has scored just three times in 51 appearances for United since announcing his arrival in 2009 with vital goals against Aston Villa and Sunderland, and has endured unproductive loans spells at Sampdoria and QPR,
He took this opportunity to catch the eye tonight, though, and it was his shot that was parried towards Javier Hernandez by Tapuwa Kapini inside the opening two minutes.
The Mexican was unable to react quickly enough, however, and the ball bounce into him before rolling wide.
Macheda broke the deadlock when he collected Dimitar Berbatov's pass and calmly found the net.
The Bulgarian was at least enjoying his deep-lying role tonight, though, and met makeshift left-back Robbie Brady's astute corner kick perfectly on the edge of the area, thundering a volley goalwards that Kapini did well to touch over.
Of the United youngsters on show, Warrington-born teenager Jesse Lingard started well but faded and the experiment of converting Irish under-21 international Brady into a fullback showed promise.
Highly-regarded 18-year-old Tyler Blackett was also given a taste of first-team action.
Meanwhile Chelsea new boys Eden Hazard and Marko Marin were both on target as the Blues began their pre-season tour of the United States with a 4-2 victory over the Seattle Sounders on Wednesday night.
Belgian teenager Romelu Lukaku led the line impressively at CenturyLink Field, opening the scoring in the third minute after being put through by Josh McEachran and grabbing another two minutes before half-time.
Hazard's deflected effort in the 10th minute put the European champions two goals up, before Fredy Montero's brace - the first of which came following a misplaced McEachran pass - got the Sounders back on level terms.
However, Marin marked his debut with a fine strike to put Roberto di Matteo's side ahead again in the 39th minute and Lukaku rounded off an entertaining first half with a fourth goal four minutes later.
Di Matteo made seven changes at the interval, including the introduction of Kevin De Bruyne, but there were no further goals.
Chelsea now head to New York to face Paris St Germain - coached by former Blues boss Carlo Ancelotti - on Sunday in what will be the first football match at the new Yankee Stadium.
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