It’s no secret that, as good as they currently look, the Celtics are getting older. Even if the “Big Three” manages to hang banner No. 18 in the Garden next spring, the team’s going to start looking very different, very soon.


Before too many seasons are out, Ray Allen, Kevin Garnett and Paul Pierce will be former Celtics (and at least No. 34 will be hanging from the rafters).


That’s when Rajon Rondo’s five-year contract extension will really start paying off. With a deal in place, Rondo can simply learn, grow and play without the pressure of being the team’s top option, or having a big-money market run on the horizon.


The $55 million the C’s will reportedly pay the point guard is a lot, but it doesn’t put Rondo in the top tier of NBA earners as he enters his prime. When it’s time for the point guard to take the reins, he’ll be ready — and he’ll be here.