United kickoff their Premier League title defence at Swansea this weekend.
"I don't think United have had their best pre-season - that is fair to say," Vorm told the South Wales Echo.
"But it is still Man Utd and they have so many quality players. They know how it is to win the league and they know how to deal with the pressure even when they are struggling a bit.
"Obviously for them, maybe it would have been better for them if they had started with a home game than away against us.
"But still the Premier League is something special; even if you had a good pre-season or a bad pre-season it doesn't really matter. We have a very good feeling about ourselves right now and they might have a different feeling, but they also know what to do to make sure they are in top form.
"If they start this season well they know no one will mention their summer. Two or three weeks can change a lot of things."
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