What does this prove?
Colyer's 25, in his absolute prime. A serious runner, who really really suits today's game.
Watson's 32, and before having last year off he'd had 2 seasons in a row destroyed by soft tissue injuries. And he's a big, heavy guy who's always struggled a bit with the running.
They're two totally different guys in two totally different situations, this is almost certainly not a 'one size fits all' scenario.
Even without the extraneous circumstances, old guys hit the wall every single year. We've got 4 of them, odds are 1 or 2 won't make it through this year.