Don't know what it is with Dan - and I follow him. Long Covid, lack of concentration , injury, end of year. But I think he's not playing to the level he can.
Yes, he doesn't seem to have the stamina he had at one time. Consitutionally he was probably affected by covid, + being double vaxxed on top of having covid knocks some people about.
I don't know about the double vaxxed side of things but I was certainly knocked sideways for about six months after contracting Covid. I wouldn't be surprised if it had an effect on elite sports people, just knocking off that extra edge.