At 27, could the Arsenal captain's best years already be behind him?
Perversely, part of Vermaelen's perceived problem is how extremely well—and quickly—he settled into the side and into the Premier League when he joined Arsenal in 2009.
Scoring on his debut and showing the kind of combative spirit, drive and leadership qualities many felt Arsenal were lacking, Vermaelen immediately became a firm fan favourite, as well as one of the most important members of the team.
His debut season was rounded off by being included in the 2009/10 PFA Premier League Team of the Year.
Unfortunately, in a certain sense it's been downhill from there.
Vermaelen suffered an untimely and serious Achilles injury at the start of the next season, which ruled him out for most of the 2010/11 campaign and part of 2011/12.
The injury cost him the Belgium captaincy, which he was unable to win back from Vincent Kompany on his return. As ESPN reported, the decision caught Vermaelen by surprise, and in retrospect it may have been the first sign that the defender's career was heading in the wrong direction.
Vermaelen has stayed injury-free for the majority of the 2012/13 season, but for the first time, it is sometimes his presence in the back four rather than his absence that can pose a threat to the Arsenal defence.
Physically, Vermaelen remains strong and committed, so his shortcomings cannot be attributed to returning from long-term injury.
Instead, it seems a worrying lack of judgment is beginning to affect his game. His lapses in the recent loss to Spurs illustrate this perfectly, with indecisive positioning, poor decision-making and lack of defensive organization leading directly to both Tottenham's goals.
Opta stats show that Vermaelen has become one of the most error-prone defenders in the league (joint third) while actually improving certain technical skills (his tackle success rate is up, for example).
But the stats in which Vermaelen has weakened indicate the nature of the problem: again, in judgment and positioning. He is making drastically fewer interceptions and is getting dribbled past more easily.
Normally, when we think of a player's decline, we focus on the physical downside. Pace, power, the loss of physical courage sometimes witnessed as players become aware their careers are drawing to a close—these are the usual areas where footballers' declines can centre.
But in Vermaelen's case, it may be a simple example of shortcomings being exposed. Without somehow addressing his organizational frailties, Thomas Vermaelen's best years could definitely be behind him.