Mourinho's two-and-a-half year tenure at Old Trafford saw United lift both the Carabao Cup and Europa. He was dismissed following United's 3-1 loss at Liverpool last December amid a poor run of Premier League results.
He made his debut for his new club in Sunday's 1-1 draw at Marseille. "It was tricky for me to leave after 13 years in England. I started my career there, won a lot of trophies, played for two top clubs, and made more than 500 appearances.
"It's nice to start the new season with a win," Spartak manager Dmitry Alenichev said. "I set my players a task to score an early opener and they achieved that. It helped us a great deal, while our third goal decided the game."
This is a great move for me and I can't wait to get started in pre-season." The deal for £51.1million comes after a stunning spell in Germany where he scored 86 goals in 89 games in two-and-a-half seasons with Dortmund.
The Premier League side found themselves behind after Diogo Dalot gave the ball away and Lens' Florian Sotoca rifled a brilliant lob past Onana from just inside the United half.
The 23-year-old has not played for Manchester United since August due to a falling out with manager Erik Ten Hag and on Thursday finalised a loan deal to return to the Signal Iduna Park until the end of the season, two-and-a-half years after
Yamal's effort was scooped from the goalmouth by Madrid goalkeeper Andrey Lunin at 1-1 in the first half and with no goal-line technology in LaLiga, VAR ruled that the shot did not cross the line.
"And probably he does it with the intention of creating a different temperature for the second half, because the game until then was really soft, in my opinion."
And Caicedo has stressed he is eager to improve as he looks to help Chelsea secure their first win of the new season. He said on Instagram: "It wasn't the debut that I expected but I'm happy to get my first minutes with this big club.