With his contract set to expire at the end of next season, there are plans afoot to extend the deal.
But Murphy believes he will need something to show for his time at the club so far – or the Old Trafford supremos will cut his time short.
Speaking on talkSPORT, the ex-England midfielder said: “They can’t be blaming tiredness for a loss at Leicester in the FA Cup and their squad not being strong enough.
“Not progressing in the Champions League was a massive, massive blow for them. Yes, they’re going to get in the top four… but so they damn should!
“He’s in a position for me where the Europa League, for me, has become monumental for him and the club.
“If they don’t win the Europa League and only finish in the top four then I think they’ll make a change.”