The Chile international saw his penalty saved in the 68th minute but he scored when the ball came back off goalkeeper Jonas Lossl.
Sanchez, 29, joined United from Arsenal during the January transfer window, with Henrikh Mkhitaryan moving in the opposite direction.
The forward impressed in his first outing for Jose Mourinho’s team in last week’s FA Cup tie away to lowly Yeovil but was quiet in United’s midweek defeat by Tottenham at Wembley.
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