It's just that, is it possible that at his current age, he can compete fully? I don't think so, it will definitely affect the stability of the performance. But I personally still really expect that he will be right here.
It's also possible they're not looking for his on-field performance as mentioned above. It's not new, I recall Liverpool doing the same thing with Milner. I suppose a team player who can lead and be vocal in the dressing room is essential. I believe a one-year contract for old but key players is also common. Most of the time they become the second or third choice for the captain position. I think it's a good deal if their goal is to rejuvenate the squad with new leaders for the future. CMIIW.