is this a keeper league, i presume? if so, how many keepers do you have going forward?
IMHO, if you're going to keep britton and picture him to be a "future ace" (which is quite a bit of a stretch... he's a nice-lil pitch-to-contact guy who has enjoyed a nice first go around the league, but as his last start shows there is some downside a-comin') then i wouldn't be too OMFG to drop him for pagan, seeing as you figure britton would have more value in the years to come. then again with rizzo, who knows what you'll get? someone like hosmer is usually the exception as opposed to the rule (~.290/5/17 in his first 100 at bats translates to ~.290/30/98 or something, if you use 6 as a multiplier figuring there's roughly 600 at bats in a full season) and hosmer has had his up and downs... clearly you're a man who's thinking ahead as you already have robbie cano at 2nd and you have lawrie, granted lawrie is playing 3B in the minors and hitting like a 3B and placido polanco is a nice lil stopgap at 3B who won't KILL you, but likely won't help you all that much either, save the sporadic game which maybe adds to a winning week in H2H or something.
however, if you're doing it for rizzo and want to jump in and keep rizzo, well then, i could see that. i mean personally, i'd sooner cut bartolo or cy correia as i think they're both further in over their heads than britton (who is over his head) -- altho i can see with masterson quickly coming back to earth and looking like, well, justin masterson, you'd want to keep on riding the hot hand i spose. clearly, if you're building for the future you make a hard choice and prolly cut colon, but that's an if... i really don't know if you're playing for this year or playing for a keeper-infused-future, which makes a lot of difference in giving you the best advice possible here.
speaking of masterson, take a look at mine would ye?! viewtopic.php?f=26&t=432547