For all his accomplishments and pedigree, Tuukka Rask has never been a full-time, No. 1 NHL goalie. The short-term contract Rask agreed to Thursday reflects both the optimism and caution with which the Bruins view the 25-year-old.

Rask agreed in principle to a one-year, $3.5 million extension, according to two sources familiar with the negotiations. He will officially sign the contract Sunday. On the same day, Chris Kelly will sign his four-year, $12 million extension.