Sanchez signed for the Red Devils from Arsenal in January in a straight swap deal Henrikh Mkhitaryan. He has scored one goal in nine games for his new club.
Club-record signing Pogba has endured a difficult spell at Old Trafford after being dropped for Premier League and Champions League matches throughout February.
The Frenchman missed Saturday’s derby win over Liverpool through injury and faces a nervous wait to see whether he is fit enough to return in Tuesday’s last-16 return leg against Sevilla.
But even if Pogba is available, Nicholas doubts whether the midfielder justifies a place in United’s team on current form, as he has ‘suffered from the confusion’ that Sanchez’s arrival has brought to Old Trafford.
‘This might not be as big for the fans, but this is as big as Saturday in terms of it being huge for them to be in Champions League quarter-finals,’ Nicholas told Sky Sports.
‘I am expecting United to go through, mainly because this is the poorest Sevilla side in years.
‘Even if Paul Pogba was fit I don’t think he would get in the United team, as he has suffered from the confusion that Alexis Sanchez’s arrival has brought to the team.
‘Antony Martial has suffered as well but it is their biggest young talent, Marcus Rashford, who has suffered the most.
‘He came in for a big game and did the business, but I wouldn’t be surprised if he’s back on the bench. I don’t know whether he’s going to play.
Manchester United 2017/18 Fixtures
Sevilla – Champions League (H) – Tue Mar 13
Brighton – FA Cup (H) – Sat Mar 17
Swansea (H) – Sat Mar 31
Manchester City (A) – Sat April 7
West Brom (H) – Sun April 15
Bournemouth (A) – Sat April 21
Arsenal (H) – Sun April 29
‘I don’t know whether Sanchez deserves to be in the line-up but if he is then it certainly shouldn’t be at Rashford’s expense.’
Frank Lampard, the former Chelsea and England midfielder, also doubts whether Pogba deserves an immediate return to United’s starting line-up.
Speaking on Match of the Day, he said: ‘I think the withdrawal of Paul Pogba sort of fell into Jose Mourinho’s lap in terms of team selection.
‘We have all been speaking recently about can he get his best players in his best positions in the starting eleven.
‘I think he managed to do that [against Liverpool] and he managed to get a better balance in the team as a whole.
‘Players knew their jobs without the ball and that’s what Jose Mourinho wants from his players. Matic and McTominay were disciplined in midfield and they set out from the start like that.
‘Those two in front of the back four, that is a job Pogba would struggle to do, especially in these big games. They shielded the back four and were aggressive.’