Jesse Lingard, Ander Herrera, Ashley Young and Marcus Rojo were all absent from Manchester United training on Monday morning, but Paul Pogba looked in high spirits.
Pogba's rift with Jose Mourinho caught the headlines last week after the Portuguese stripped the midfielder of the vice-captaincy and the pair clashed at United's Carrington training complex.
However, the France international started against West Ham, although he was substituted in the second half after an under-whelming performance, and was photographed smiling while warming up for training on Monday.
Former United players have been suggesting that Mourinho appears to have lost the dressing room and Louis Saha is the latest to have criticised the Red Devils' performances under the current manager, claiming they play 'boring, unexciting football'.
There have even been reports that the European fixture on Tuesday night is a must-win game for Mourinho amid speculation the manager could lose his job should his side fail to perform.
Fans were left in uproar after the last Champions League night at Old Trafford when United were shocked by a 2-1 defeat to Sevilla in the round of 16 second leg that sent them crashing out of Europe last season.
This campaign, the Red Devils picked up a win in their first Champions League group match against Young Boys on September 19 but Valencia will pose a much more difficult challenge, ahead of a double-header against Cristiano Ronaldo's Juventus.
Following the game against Valencia, United will face struggling Newcastle at home in the Premier League in their final fixture before the upcoming international break.