Carl Jenkinson was doing very well until this season. His boyhood passion for Arsenal made him a fan-favorite, as did his incredible work rate (probably derived from his passion for the club) and a wicked ability to cross the ball into the box.
He was raw, sure, unfinished defensively with noticeable kinks to work out at both ends of the pitch. But Jenko, as he is affectionately called, was (and still is) a young player with plenty of time to work on his game.
So he deputized for Bacary Sagna for three years, getting significant game time when the Frenchman broke his leg on two separate occasions and in cup matches but was somewhat hampered by occasional medium-term injuries.
When Jenkinson arrived at Arsenal in 2011, he was completely unready for first-team football at the highest level, but he largely learned by doing. He progressed on the pitch, but when he would re-emerge from a prolonged period on the sidelines last season, there seemed to be little progression.
In other words, Jenkinson's development stagnated. The same little issues would present themselves in every fixture in which he played: failing to track back, ball-watching, failing to maintain the offside trap, etc. All of these are typical of either a young player in development or someone who just is not elite.
Jenkinson is still in the relatively early stages of his career, but he is at the age when he needs regular football to polish his skills and make his final developmental steps.
It is very telling that Arsene Wenger did not trust him with the starting right-back job when Sagna left on a free transfer to Manchester City. The timing was not quite right—perhaps one more year as an understudy would have given him enough time to earn the manager's confidence, but Sagna bolted a little too soon.
Kieran Gibbs is an excellent comparison, as he replaced Gael Clichy (after the latter's departure to Manchester City, incidentally) on the verge of his 23rd birthday. Gibbs had years of experience as a backup but, to the surprise of some, had shown enough to Wenger to warrant a promotion.
The manager's famous instincts about young players proved true again in Gibbs' case, and the club's new No. 3 is one of the best left-backs in England.
Wenger does not believe in Jenkinson's ability to contribute right now so he went out and spent a princely sum on Calum Chambers who played right-back for Southampton last season. Though Wenger has praised Chambers for his versatility and even tipped him for a role in central defense and midfield, per Arsenal.com (h/t Arseblog), Chambers' training at right-back means even fewer opportunities for Jenkinson.
His move to West Ham United on loan therefore makes a lot of sense for all parties. Sam Allardyce plays a very no-nonsense defensive style of football, and injecting some of his grit into Jenkinson can only do him good. Plus, there is no overflow at right-back.
If Wenger does not project Chambers as Arsenal's future starting right-back, Jenkinson still has an opportunity to play for Arsenal again. Mathieu Debuchy is 29 and was very likely bought as a short-term solution until a younger player steps up to fill the role for several years.
But Jenkinson now faces competition from Hector Bellerin as well as Chambers. And the Spaniard, who has been massively impressive in the Emirates Cup, seems brimming with potential at only 19 years old.
Moreover, Bellerin will have the opportunity to directly impress Arsenal's coaching staff for the U-21 team and/or the Reserves this season.
The Gunners will no doubt be monitoring Jenkinson from across London, but he will have to explosively develop this year to have much chance of suiting up for his boyhood club again.