As usual, all numbers cited in this posting were found on fangraphs.com and ownership rates are from Yahoo! Fantasy.
Currently owned in 12% of leagues. He is being picked up as more of a speculative play as it was announced that regular closer Koji Uehara may possibly be shut down for the season.
In the event that Mujica becomes the Red Sox closer to close out the season, is it going to work out (beyond some potential saves)? While he does have some closing experience ( he saved 37 games for the Cardinals last year), my answer is no.
He does sport a 4.13 ERA this year (with a 3.76 FIP & 3.75 xFIP) so he isn't exactly dominating the opposition, This isn't just a fluke year as these totals are not too far off of what he's done in his career. He's also not going to make up for it in strikeouts as he's only struck out 6.7 per 9 this year (7.1 in his career). While it's likely he'll continue to get picked up by players that are absolutely desperate for saves, there's nothing in his numbers that indicates that he would be able to hold down the closer job for an extended period of time.
Currently owned in 2% of leagues. He has primarily been in middle relief this year (thus the low ownership rate). He was pushed into spot-starting duty last Saturday against the A's and struck out 6 batters in three innings. It was announced that he will be starting this Saturday's game against the Twins. Besides playing a weak opponent what are the chances that Rasmus could be a good pickup.
While, there is the concern over him being stretched out enough to go deep into ballgames, there are some encouraging signs that you can get a good performance out of him during the innings that he is in the ballgame.
While his 2.48 ERA is overly-optimistic going forward, the advanced numbers indicate that he could be a solid starting option assuming he's able to cover more innings as his FIP & xFIP (2.80/3.27) are both very solid and he also looks to be a solid source of strikeouts (9.9 per 9 innings this year).
Jorge De La Rosa:
Currently owned in 26% of leagues and the owner of a nice 2 year/$25 million extension. He has been getting picked up today but it seems a bit perplexing why. Despite having 13 wins, he isn't necessarily on a hot streak, he pitches his home games at Coors Field (though in all fairness has somehow pitched much better at home) and he doesn't necessarily make up for his very pedestrian ERA (4.26) with a bunch of strikeouts. If anything, he is lucking out in this area as his BABIP .263 is much lower than his career total .300.
The Rockies, a team already in shambles could be in even more shambles if his luck on batted balls goes away.