Owen Hargreaves was among four first-team regulars missing from the Manchester United squad that set off for their pre-season tour to South Africa on Thursday.
United manager Sir Alex Ferguson has selected a 21-man squad for the four-match trip, but Hargreaves, Edwin van der Sar, Patrice Evra and Nani did not board the flight to Cape Town. England midfielder Hargreaves missed Saturday's friendly at Aberdeen with a knee injury, while Portugal winger Nani, Dutch goalkeeper van der Sar and France left-back Evra have all been excused after playing at UEFA EURO 2008.
Cristiano Ronaldo had already been ruled out following his ankle operation. Ferguson confirmed Hargreaves has the same tendinitis problem which forced him to have pain-killing injections to ease the problem last season.
"It was apparent as soon as he came back to training. It is the same as last year. Some people get these things," Ferguson said. "Maybe re-starting training on the firmish grounds brings it on or maybe it is just an inherent problem.
"We are trying to sort it out now with injections. That is what we did last November and it worked. Hopefully these work and by the time we come back from South Africa he should be okay. Owen is not written off for the start of the season at all. I am sure he will be okay."
There will still be plenty of United stars on show, with Wayne Rooney, Carlos Tevez and Ryan Giggs making the trip along with skipper Gary Neville, who made just one first-team appearance last season due to an ankle problem.
Neville is now fully fit after 16 months on the sidelines and Ferguson expects the England defender to use the tour to push Wes Brown for the right-back position.
"For Gary in particular this trip is very important. He came through his 45 minutes at Aberdeen on Saturday with no problem at all, which is fantastic news," Ferguson said. "The great thing about Gary is that he has not missed a training session since the last time he came back in April.
"We could have played him at the end of the season but Wes was doing so well. His form was so good I didn't want to have doubts in my mind about picking him. Wes had played in every game, so we kept it like that. But now, a new season is about to start and Gary will get his chance."
United play Kaizer Chiefs at Cape Town's Newlands Stadium on Saturday, then face Orlando Pirates in Durban on 22 July before playing one of the two South Africa sides again at Loftus Stadium four days later. The tour concludes with a friendly in Abuja, Nigeria, against FA Cup winners Portsmouth on 27 July.