The Chile international moved to the Red Devils in a swap deal from their bitter rivals Arsenal in the January transfer window.
Sanchez completed a surprise move to Manchester United from Arsenal despite previously being linked with Manchester City.
The South American forward only scored one goal in 11 games in all competitions to make a slow start to life at Old Trafford.
The 28-year-old second goal in 11 outings when Manchester United eased to a 2-0 win over Swansea City last weekend.
Former Manchester United defender Neville believes Sanchez has been dropping too deep into midfield to hamper his ability to impact the game.
“I have been critical of Sanchez in recent weeks for coming too deep,” Neville told Sky Sports. “Get in where it hurts.”
Manchester United finished in sixth place in the Premier League table last season but won the EFL Cup and the Europa League.
The Red Devils side suffered a surprise 2-1 loss to La Liga outfit Sevilla in the Champions League round of 16 last month.
Sanchez won two FA Cup titles in three seasons during his spell at Arsenal following his move to The Emirates from FC Barcelona in 2014.
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