Next season would've been his senior year, and he probably would've played a pretty big role in any sort of BC revival. He's been a nearly 30-minute-per-game player ever since he arrived on campus, and averaged 11 points last season. He wasn't a massive part of BC's team, but losing a senior starter and major contributor from an already-struggling team can't be good.
It also hurts because Boston College really had (or still has, some would argue) the chance to be a surprise ACC contender next season. They'd return literally almost everything - over 90% of their scoring and all 5 starters would've been returning had Sanders stayed on board. Combined with a new vigor around the program and a new coach, it looked like the Eagles could've done some damage.
Now that he's gone, it's almost BC doesn't have their Sean Mosley - Sanders is far more active offensively, but Mosley does more on defense on the glass, so their contributions were probably similar. Sanders' departing isn't a dagger to those comeback hopes, but it's certainly a hindrance. Regardless, it's good news for Maryland.
Now, is Kyle Singler next? Hopefully.
Note: Once he makes his decision, I'll finalize the Coming and Going research and we'll get it up shortly after.