The Chile international completed a switch to Manchester United from Arsenal on Monday evening as Henrikh Mkhitaryan moved to the north London side in the same deal.
Sanchez finished as Arsenal’s leading goal-scorer last term after the 29-year-old netted 24 goals in 38 games in the Premier League.
Lukaku, on the other hand, scored 25 league goals in his final season at Everton before a £75m switch to Old Trafford.
The Belgium international scored 10 times in his opening nine games in all competitions but struggled in October and November.
Lukaku has netted 16 times in 32 games in the current campaign to make a steady if unspectacular start to life at Manchester United.
But former Chelsea winger Nevin doesn’t believe Sanchez’s arrival will put Lukaku’s spot in the team under threat.
“I don’t think he will be the main striker,” Nevin told Irish radio station Newstalk. “Lukaku will be.
‘The way Jose has played over the years, he loves a big striker.”
Sanchez won the FA Cup twice in three seasons at Arsenal before his switch to Manchester United.
The South American could make his Premier League debut for Manchester United at Tottenham Hotspur on Wednesday night.
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