Six-and-a-half years after signing with Bayern Munich, Arjen Robben has established himself as a hero of the club.
Although he's wavered at times, the Dutchman carried his side to the 2010 Champions League final and scored and assisted his side's goals in the 2013 final. When fit and in form, he's one of the most decisive players in today's game.
At the same time, Bayern must be careful to regularly reassess their star player, noting any changes that come with his increasing age. He'll turn 32 years of age later this month, the time at which acceleration on average begins to slow.
And as time passes, the question of when he will be deemed past his best and in need of replacing in the lineup is becoming more and more relevant.
At present, it's hard to tell where the Dutchman is in the aging process. Per Transfermarkt, Robben missed 29 games in 2015 and has played just 746 minutes in the current campaign. Players often become more injury-prone when they get older (Franck Ribery is a prime example and his is a cautionary tale), although Robben has never exactly been the healthiest of players.
This could just be another tough spell with injuries, just as he experienced after the 2010 World Cup and in the fall of 2011.
Still, the clock is ticking, and Robben knows it: In a recent interview with Die Welt (h/t Sky reporter Alex Chaffer), he admitted to having psychological problems throughout a "s--t year" in 2015.
He's nearing the age when the explosive burst of pace on average tends to start to falter, and figuring out how to adapt his game as he loses his quickness will be a hurdle. It's something he had to figure out in the spring of 2011 as he redeveloped strength in his hamstring that had been mangled for months prior. And he ended up having a very successful spell that spring, so it is reason to believe he'll figure out how to age with grace rather than simply "hitting the wall."
Robben has looked good in the games in which he's played this season, having scored five and assisted two goals. At a rate of one of either every 107 minutes, that's still excellent. And he commands enormous respect on the pitch.
As such, at this point it's not sensible to think about signing a player to replace the Dutchman. The January market is very inflated, and selection is limited. Moreover, it would be a silly thing to do with Kingsley Coman having had such a successful spell in Robben's absence during the first round.
It would be wiser for Bayern to wait until the summer and reassess the situation. If Robben experiences a similar downturn to Ribery's, it will force their hand: Bayern will have to make a signing, which could pose problems for the club.
They could invest heavily in a player with a few years left at a high level, which could jeopardize Coman's development. Or they could sign a young and rising talent, which would also carry risks in that youngsters often take years to become reliable and in some cases never do achieve their apparent potential. Coman can't be relied on too heavily too soon, nor can a potential young signing who'd take his place in the event of an injury or suspension.
Thus, Bayern will hope Robben has a more successful spring campaign and proves capable of carrying on for at least another season as Coman develops. Ideally, the Frenchman will play more and more minutes and Robben fewer and fewer until the student Coman eclipses the teacher, Robben.
And if it looks as though Robben is no longer capable and Coman stagnates, then Bayern can look around for other starting options. For now, though, there is no reason not to stick with Robben.