Wayne Rooney thinks Danny Welbeck did the right thing by leaving Manchester United for Arsenal this summer.

Many United fans were shocked earlier this year when Louis van Gaal sanctioned Welbeck's £16million transfer to the north London club.

Welbeck is a life-long United fan and joined the club as an eight-year-old having grown up locally.

During his 11-year spell at United, Rooney watched the pacy forward progress from teenage prodigy to first-team striker and admits it will be strange to play against the 23-year-old striker when the Red Devils travel to the Emirates Stadium today.

"Of course, Danny has been here all of his life," Rooney said "He is a Manchester lad so it is weird seeing him [there].

"But that's football nowadays and players move on."

Rooney, who played alongside Welbeck for England against Slovenia and Scotland in the recent international break, thinks leaving United has been beneficial for his former team-mate.

"I think, for Danny, and for his own personal career, it was probably the best move for him," Rooney said.

"He's done great and scored a few goals and is playing well. Danny gives you what he always gives you - a good shift. He works hard for the team.

"At times, as I said to him, he works a bit too hard but he's scoring goals and he's doing well."

Arsenal against United has been one of the biggest fixtures on the calendar in recent years, but neither side is considered a serious title contender this season.

For Rooney, the fixture still brings back fond memories, though.

"We've had some great memories," the England captain added.

"Beating them in the Champions League semi-final (in 2009) was probably the highlight."

Van Gaal has been hit by an injury crisis on the eve of the match.

Radamel Falcao, Daley Blind, Jonny Evans, Phil Jones, Marcos Rojo and Rafael are all out so Chris Smalling is likely to be partnered at centre- back by teenager Paddy McNair.