Sanchez made his Premier League debut for Manchester United last night, and despite playing the full 90 minutes, he was unable to prevent his side falling to a 2-0 defeat away to Tottenham.
A Christian Eriksen strike after just 11 seconds and a Phil Jones own goal made it a miserable evening for Mourinho’s men.
Sanchez had little impact on the game, although he showed the usual grit and determination associated with the Chilean.
And while Mourinho acknowledged Sanchez’s graft, he admitted he was unable to quite click into gear with Romelu Lukaku.
Discussing Sanchez’s display, Mourinho said: “He worked hard, but again the transformation the game had, the game was not for him.
“In the second half, I tried to give him a position where he could be closer to [Romelu] Lukaku but then he felt the need to drop too much to organise.
“But he gave everything, good effort and this is a good feeling for me to know that the player is available with that spirit.”
United’s defeat leaves them 15 points adrift of table-toppers Manchester City.
They will hope to get back to winning ways at home to Huddersfield on Saturday (3pm).