In short, that management doesn't think very highly of Boone Logan. Before we delve into that though, let's look at what Manny's done at Double-A.
If you didn't see in Brandon's post, Manny Banuelos is being promoted to Triple-A Scranton to start tomorrow.
Frankly, I'm very surprised (and not the only one) that they're promoting the 20-year-old southpaw. Between him and Dellin Betances, another highly touted pitching prospect on the same team, Betances was having a markedly better season. Now don't get me wrong, Manny's having a fine season: 95.1 ip, 3.59 ERA, 94 K, 52 BB, 94 h, 50 GB%. But not only has Betances been better (89.1 ip, 3.43 ERA, 98 K, 49 BB, 64 h, 52% GB)*, but he's three years older, meaning his "prospect glow" will sooner wear off. You'll notice the biggest difference is the hit rate. All the other stats are similar, but Betances has been significantly better at (dis)allowing hits. That, coupled with his age, and we have to wonder why Mark Newman and Brian Cashman would choose Manny over Dellin. It probably all has to do with handedness.
The aforementioned Logan has struggled against fellow lefties this year. He has a much better K:BB rate against them (22:5 vs. 7:5), but they've also hit him much harder (.761 OPS vs. .556 OPS). That's where Manny comes in. He's struggled against RHB this year, but has mostly dominated LHB. The splits:
Vs. RHB - 66.1 ip, 4.61 ERA, 62:41 K:BB, 1.2 Ground-outs:Air-outs
Vs. LHB - 29 ip, 1.24 ERA, 32:11 K:BB, 2.1 GO:AO
Knowing this, it seems that a plan to get Manny's feet wet in Triple-A could be a precursor to a late-season call-up to pitch out of the Bronx bullpen. Since he's never thrown more than 109 pro innings in a season, he might get about three Triple-A starts (at 5 ip/start, he'll be right at 110 ip) before a conversion to the bullpen to 1) be the new/better? LOOGY, 2) get ML experience, and 3) ease him toward an innings cap.**
* What's frustrating is comparing the Trenton stats of Manny and Dellin to Phil Hughes, who utterly destroyed Double-A at the same age as Manny (116 ip, 2.25 ERA, 138 K, 32 BB, 73 h), yet has failed to find consistent success as a starter in the majors.
** While I'm speaking of prospects, look at what recent first-round pick Dante Bichette, Jr.'s been doing in the Gulf Coast League. Then compare that to what way-more-highly-touted prospect Jesus Montero did at the same level (albeit a year younger). It pales in comparison to DBJ.