According to Keith Law, the Cubs have acquired Jacob Turner from the Marlins for “a couple of minor leaguers”. Turner was a pretty high profile prospect a few years ago, is just 23, and this acquisition falls in line with the Cubs buying low on young pitching and seeing what sticks. Assuming the two minor leaguers have minimal value, this is probably a decent enough move by the Cubs, because young arms sometimes turn into Jake Arrieta.

But before we throw the Cubs a parade for acquiring Turner, let’s maybe point out something of importance: the current version of Jacob Turner does not belong in a Major League rotation, and barring some dramatic improvement from either his change-up or his curveball, he profiles best as a middle reliever.

Since the start of the 2011 season, 149 pitchers have thrown at least 100 innings against left-handed batters. By K%-BB%, Turner ranks 147th. Here are his peers in controlling the strike zone against lefties.

Name	K%	BB%	K-BB%	xFIP
Jason Marquis	12%	13%	-1%	5.26
Luis Mendoza	11%	11%	1%	4.88
Jacob Turner	12%	11%	1%	4.82
Jhoulys Chacin	12%	11%	1%	4.82
Jake Westbrook	10%	8%	2%	4.68

Marquis is a replacement level scrub at the end of his career. Mendoza is a swing guy who makes spot starts when someone is hurt. Westbrook is out of baseball. The only guy in this mix who has had any real value of late is Chacin, who has succeed by limiting BABIP and HR/FB ratio while pitching in Colorado. Turner hasn’t shown the same ability to limit hard contact, and his results have actually been worse than his also-bad peripherals.

Yes, Turner is 23, and yes, there’s plenty of time for him to live up to the promise he showed as a minor leaguer. Maybe the change-up will get better and he’ll have a real weapon against left-handers someday. He doesn’t right now, though, and until he does, he’s going to project as a reliever, and not even the kind of reliever you can trust with full-inning, high-leverage appearances.