The Chile international has struggled since his controversial transfer to Manchester United from Arsenal in the January transfer window.
Sanchez has only managed to score four goals in 16 appearances in all competition to prompt some criticism of the South American.
The Manchester United striker didn’t get on the score sheet in their dramatic 2-1 win over his former club Arsenal at Old Trafford on Sunday.
Sanchez moved to the Red Devils to become the Premier League’s best-paid player after he failed to agree a new contract with the Gunners.
The January signing started ahead of England international Marcus Rashford and France forward Anthony Martial for the visit of Arsenal.
Former Liverpool FC captain Redknapp raised questions about Sanchez following another subdued performance at the weekend.
“There are a lot of questions about what their best 11 is,” Redknapp told Sky Sports.
“Alexis Sanchez is a shadow of the Sanchez I saw at Arsenal. Martial and Rashford, they have to find a way to get them in the team. I think they’re too good not to be in this team.”
Sanchez scored 24 goals in 38 games in his final season at Arsenal before his controversial switch to Manchester United.
The Red Devils are in second place in the Premier League table to make a marked improvement upon their sixth-placed finish in Mourinho’s first season in charge.
Manchester United lost 2-1 to Sevilla in the Champions League round of 16.
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