Mannone was not as useless as the likes of Park Chu-Young, Nicklas Bendtner or Marouane Chamakh. Those men did absolutely nothing, were loaned out to other clubs and proceeded to do more of absolutely nothing.
The Italian, on the other hand, made 13 appearances for the Gunners last season in the absence of both Wojciech Szczesny and Lukasz Fabianski. While he did not display the assertiveness or intangible qualities of a first-choice goalkeeper, he was perfectly serviceable and performed his task capably.
That said, his time at Arsenal was up.
After seasons of producing little on the pitch and evidently showing few signs to Arsenal's staff that he is capable of doing so, Mannone was mercifully given the chance to build a successful career at a club where he can exhibit his talents.
Good for him.
But his sale has produced a ripple that could affect Arsenal's transfer business this summer.
For now, the club only has two senior goalkeepers on the roster. Netminders obviously suffer fewer injuries than their running teammates, but almost every squad includes three of these specialists.
After all, Arsenal did require the backup to their backup to put on his gloves and get between the posts more than a dozen times just last season.
A goalkeeping acquisition must therefore be made. Youngster Damian Martinez is not yet ready to make the jump to senior football, and his development would be stunted by heating the bench while Szczesny starts.
The Brazilian, who was one of Brazil's brightest and most surprising stars during their spotless Confederations Cup triumph, has been strongly linked with Arsenal by the Daily Mail, and it is not difficult to see why—it just makes sense.
Arsenal have long been without an experienced backup goalkeeper whose inclusion in the starting XI would not give fans palpitations.
At 33, Cesar has the requisite CV: a highly successful seven-year stint with Inter Milan during which he won the Champions League, 74 caps for Brazil to date and a full season of Premier League polish with QPR.
He would be eminently capable of mentoring Szczesny if he is willing to accept this role. Moreover, his obvious quality would keep Szczesny on his toes and ensure healthy competition within the team.
When he and Fabianski jousted at the end of this past season, the better goalkeeper was given the opportunity to start and thus the entire club benefited.
More relevantly, though, this move actually makes sense—a relative rarity during this time of the year.
And, according to Goal, QPR manager Harry Redknapp has confirmed that Cesar will move on before the commencement of next season, saying, "He won’t want to play in the Championship, he’s a goalkeeper for a big club."
Then there is the vacancy left by Mannone's departure.
That, ultimately, could have been the first domino that needed to fall for Cesar to transfer across town.
Arsenal will surely not carry three top goalkeepers on the roster next season—Fabianski has already been denied far too much playing time (though largely by injury) than his ability merits.
Arguably, that raises the entire issue again. But with two goalkeepers of Szczesny and Cesar's raw talent and experience, a cheaper third option can be acquired.
Regardless, Julio Cesar is now absolutely a realistic transfer target for Arsenal.