The Spaniard joined the Red Devils on an 18-month contract following months of training with the side in a bid to regain fitness after suffering a long-term knee injury at the end of last season.
The former Barcelona man arrives at Old Trafford with such a high pedigree, having won more than 20 titles at the Nou Camp including three Champions League triumphs.
His winning habit and the knowhow of being a champion can have a big influence on the side, and Collymore feels his experience and evident quality was the sort the Gunners have been seeking.
The North Londoners have blown hot and cold this season, and they face a tough task in finishing in the top four in the Premier League as a result of their inconsistent results earlier in the campaign.
Many observers feel a new defensive midfielder is necessary at the Gunners and has been for a long time, yet there could be a case for a new shot-stopper too.
Current number one Wojciech Szczesny has not had the finest past few weeks – making blunders at Southampton, later caught smoking and then being dropped for the victory over Stoke City.
Collymore believes he needs replacing, and makes a point that United’s new acquisition would have been the ideal man for the job.
"Szczesny picked up a fine for his naughty cigarette but he is lucky Arsenal haven’t gone straight out and found a replacement,” he wrote in the Mirror. “He’s hardly been in great form.”
“In my opinion the club should have got Victor Valdes and shown Szczesny what it takes to be a winner.
“That’s the problem with many of this Gunners team, they’re not ruthless enough. They don’t have the mental strength to get through tough stages of a season. There is no real leader.
“Valdes would have loved to live in London. So why not get him in?”