Old for the league? It's AAA, which is filled with everything from 20-21 year olds who have graduated from AA, to 30 y/o AAAA players stashed as injury replacements. He's middle of the road in terms of age.
And, the only reason he's old in the sense that you are using it, ie "it took him until his age 27 season to reach AAA", is because of his unique career track taking him through the Independent Leagues. After that: one year in A ball, one year in A+/AA, one year in AAA. No stumbling along the way.