Steve Bulpett of the Boston Herald reports:

Celtics will sign Rajon Rondo to extension

The Celtics and Rajon Rondo walked close to the edge of the bridge with their contract negotiations. But while each was confident it could pull off a successful dive, neither really wanted to jump.

By agreeing to an extension that will pay Rondo some $55 million over the five seasons after this, there was security for all. Or about as much as the rigors of the NBA and the global economy allow.

Indeed, the Celtics could have easily let the season play out, secure in the knowledge that they could make Rondo the qualifying offer after the year and thus render him a restricted free agent. They could then let the market do its thing and match any offer that came his way.

No matter the final numbers, Danny Ainge and the owners knew that Rondo would be a Boston Celtic next season if they so desired.

Once the deal is signed, it’ll be interesting to watch Rondo’s growth in the future. Lots of players, not by coincidence, seem to stop getting better starting the season after the one in which they sign a big contract extension. Hopefully Rondo keeps improving in years to come.