Northern Irishman Evans suffered a back problem during Saturday's 3-1 win at Fulham in the Premier League, while Brazilian Rafael hurt his ankle also in the first half.
There was better news for midfielder Tom Cleverley, who came off at halftime at the weekend with double vision, because he has recovered in time for the match at the Anoeta stadium.
"We haven't had a lot of injuries," Moyes told a news conference in San Sebastian. "I think it's the best Manchester United have been in that respect for a while. But we did pick up three on Saturday, which is very rare - especially by halftime.
"Two of them haven't travelled - Jonny Evans and Rafael (are) not with us."
United lead the group with seven points from three matches, one point ahead of Bayer Leverkusen. Shakhtar Donetsk are third on four while Real Sociedad are bottom with no points.
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- Manchester United
- Tom Cleverley
- Jonny Evans
- Premier League