The 20-time league champions have won just one of their last four Premier League matches, and suffered one of their worst defeats of the season by losing 2-1 at lowly Sunderland on Saturday.
Van Gaal has received a lot of criticism this season for his tactics and his side's poor displays in front of goal, but the Dutchman's captain Rooney is adamant that the buck should stop with the 11 players who take the field, not the man in the dugout.
He told the Mirror: "It’s a very good group of players. At times it’s been frustrating for us as we’ve under-performed, and actually the manager has taken a lot of stick for some performances.
"It’s down to us, we’re players and we have to perform. At times this season we haven’t done that. In terms of that, we’ve probably got off quite lightly and the manager has taken a lot of it.
"But we’re going on the pitch. We have to create chances and win games and we haven’t done that enough this season."
United are in danger of failing to qualify for the Champions League next season, as they currently sit fifth in the Premier League table, six points adrift of neighbours Manchester City.
They face three matches in other competitions before playing in the league again, with both legs of an Europa League last 32 tie with Danish side Midtjylland either side of an FA Cup fifth round trip to Shrewsbury Town next Monday.