Manchester, Oct 1 (IANS): Manchester United manager Louis van Gaal stressed that his players are getting tired and are suffering because of back-to-back matches.

United, who have played six matches in 18 days, won 2-1 in a Champions League clash against German side Wolfsburg on Wednesday.

Juan Mata's first-half penalty and Chris Smalling's 53rd-minute goal gave United their first victory in Group B.

United is scheduled to face Arsenal on Sunday in the English Premier League.

"A lot of players are very tired because of the accumulation of a lot of matches," Van Gaal was quoted as saying by the BBC on Thursday.

"Arsenal played yesterday -- one day more to recover. That will benefit them but we shall manage it."

United lost their first Champions League game against PSV Eindhoven, but victory over Wolfsburg means all four teams in the group are level on three points after two matches.

"We have everything in our own hands and that is very important," van Gaal said.

The Dutchman said his side showed "fantastic spirit" to recover from Daniel Caligiuri's fourth-minute goal.

"We score but after that it was suffering. Arsenal played yesterday - one day more to recover. That will benefit them but we shall manage it,” Van Gaal said.