I like a two year extension at about 5.5m per. Get the most out of what he has left, just in time for Studnicka to be really ready to go and possibly Beecher too.
I'm actually wondering whether the Bs might only offer him a 1 year extension, or possibly even nothing at all. Not because he doesn't deserve a new contract, but because I don't think the Bruins are going to want to be in a position for much longer where their top 2 centers are not just mid-30s but pushing well into the twilight zone of most players' careers. I'd say as a GM you'd be wanting to move on from Bergy and Krej one at a time, not together. The hope ideally has to be that Studnicka can fill the 2C role post-Krejci, but that's still far from certain and we're unlikely to get an answer on whether that's probable before next season. Any possibility of Coyle at least temporarily taking on that role seems to be declining. If they want to keep banking on Stud then I can envision Krej getting a short-term deal while they see if Jack can make the grade, or at least not saddling him with a contract that is immovable if necessary.
The alternative is Sweeney doesn't wait on Studnicka and he takes Krej's $7 mil and goes out and finds the best possible center he can this summer, hopefully someone who also has the potential to step up to the 1C role in time, which still keeps a possible place for Stud should he indeed prove a top 6 player.
Either way, I think Krejci's shelf life with Boston is one more year tops, and if he gets that I wouldn't be surprised if in mid-2022 he just hangs up the skates and walks away a one-team guy. It would be fitting for someone who's never really looked like ever being anything but a Bruin.