MALAYSIA -- Former Arsenal defender Sol Campbell says that Arsene Wenger's side are two defenders short of being a top team and may need "to do a Manchester United" and win the Europa League in order to secure Champions League football for next season.

Arsenal were left to rue defensive mistakes as they fell to a 3-1 home defeat against Manchester United for their fifth defeat in 15 Premier League matches this season. It left them in fifth position on the table, 15 points behind runaway leaders Manchester City.

"I think the main priority [for Arsenal] is to get back into Champions League ... they need to get back into the big time," Campbell told ESPN FC in Malaysia, where he is working as a pundit for Astro SuperSport.

"They might have to do it the Man United way -- win the Europa League. Hopefully they can do that, but it's not easy."

Campbell, who played in the Premier League for almost 20 years and was a member of Arsenal's "Invincibles," says he was heartened by their performance at the Emirates Stadium after conceding two early goals.

"They've done pretty well overall. If they can build on that performance against Manchester United -- but cut out the first 10 minutes -- they'll be OK," he said.

"But Arsenal are one, maybe two defenders short of being a top team. They really need to push the boat out and buy a couple more players."

After nine years with north London rivals Tottenham Hotspur, Campbell controversially joined Arsenal for the 2001-02 season. Initially, he was partnered in central defence by club captain Tony Adams before forming a formidable combination with Kolo Toure when Adams retired.

He says he is not a fan of the back three that Arsene Wenger has often used this season. The Arsenal boss reverted to a four-man defence after falling behind in the first half of Sunday's defeat against Man United.

"For me, I've played in a back three for England and a couple of times for Tottenham, but I can't remember ever playing that for Arsenal," he said.

"If you want more going forward, you might do 3-5-2, but I prefer a 4-4-2. And if you're fluid enough, you can be flexible enough and have enough players interchanging and going forward."

Campbell, 43, reiterated his interest in becoming the United States' head coach in the future. Earlier this year, he worked for six months as assistant boss with their CONCACAF rivals, Trinidad and Tobago.

"I'm ready for a new challenge and I'll put my head on the block. I'm a winner," he said.

"I'm successful, and I want to be a successful manager as well. If [the United States] ever came to me, I'd put my hat in the ring and I'd talk. That's how it starts."