All three were absent from the Red Devils' 2-1 win over Valencia in their final pre-season friendly, and manager Louis van Gaal revealed he would be playing a waiting game over their availability for the meeting with Swansea City on Saturday.
"We have a lot of injuries now," the Dutchman told MUTV.
"We don't have to forget that Evans was injured, Shaw was injured, Valencia was injured and these are three defenders so we have to wait and see if they can play on Saturday."
Van Gaal played the 3-5-2 system that he favoured with the Netherlands in the World Cup and on United's pre-season trip to the United States, using Reece James and Ashley Young as wing-backs.
Valencia would appear to be an option in that position, but van Gaal felt the performance from the players he was able to select for his first outing at Old Trafford was not as good as what had seen in earlier matches.
"I think it was our worst match today," he added. "We did not play to the capacity that we showed in the United States too much. There were a lot of wrong choices, wrong passes. We didn't press so good."
Maraouane Fellaini struck in injury time at the end of the match to hand United victory over the Spanish outfit, the Belgian having been a late substitute along with fellow countryman Adnan Januzaj.
"We are at this moment fitter than our opponents and you could see that and also the (substitutions) helped of course. Now Fellaini and Januzaj have only been with us one week, one and a half weeks, so they cannot play more minutes.
"They did reasonably well but they can do better I believe, but it is a start for them and also there were four debuts today. It's not easy to play at Old Trafford for the first time so I'm pleased with how they have done against a very good team."