D.C. United and MLS All-Star manager Wayne Rooney was highly critical of his team's preparations ahead of their 5-0 thrashing to Arsenal at Audi Field in Washington, D.C on Wednesday.

Arsenal's new midfield star Declan Rice made his first appearance for the club as Gabriel Jesus, Leandro Trossard, Jorginho, Gabriel Martinelli and Kai Havertz all scored for the Premier League side.

- Stream on ESPN+: LaLiga, Bundesliga, more (U.S.)

Although the MLS All-Stars had previously defeated the likes of Chelsea and Bayern Munich in this format, Rooney's squad -- which did not include recent Miami addition Lionel Messi -- struggled, and he hit out at the training facilities.

Asked what he learned from the match, Rooney told a postmatch news conference: "Absolutely nothing. Listen, it's difficult. On Monday the players all arrived and we did a small-sided game.

"On Tuesday, as I suggested, I didn't want them training at the National Mall but that's where we trained and we can't do anything.

"We did head tennis so literally had no time whatsoever to do any tactics whatsoever, so you put the players out there and you hope they can figure things out, and against a team like Arsenal that's very difficult to do."

He added: "The result is what it is. I was a little shocked at the quality. The lads were nervous and hesitant to get shots off and I think here you see the difference between All-Stars and one of the best teams in Europe."

The former Manchester United captain also critcised the standard of refereeing in the league after he saw four of his players receive yellow cards before half time.

"I thought the referee made the game a little bit about himself once again," Rooney added. "I think that's something that needs improving in the MLS. I've said it all season, so it's a good opportunity for me to bring it up again."

Preparing for their Premier League opener against Nottingham Forest on Aug. 12, Arsenal play friendlies against Manchester United on Saturday at East Rutherford, New Jersey, and against Barcelona on July 26 at Inglewood, California.

Information from The Associated Press was used in this report.