Manchester United boss Louis van Gaal has admitted that he was disappointed with his side's performance in their pre-season victory over Roma.
A first-half brace from Wayne Rooney and a strike from Juan Mata had given United a comfortable lead.
However, the Serie A side gave the Red Devils a late scare with a goal from Miralem Pjanic and a penalty from Francesco Totti.
Van Gaal told the club's official website: "I am pleased that we have won but it was not a good performance, 54,000 people came to watch us but we can perform much better.
"We are not used to this hot weather. I think we didn't play a good match because of the height of the stadium, the air, because all my good passers failed today.
"When you are 3-0 ahead, the only thing you have to do is keep the ball in possession and then the opponent has to run and run and run. It's very difficult in this hot weather to do that."
United play Inter Milan in their next pre-season game on Wednesday.
