What I'm Watching: K/BB Rate

Some sabermetric analysts have mentioned K/BB rate as the most important rate stat to view when considering a pitcher. I don't remember which ones said that, but it's definitely an important number. The ratio gives us something of a common denominator to compare pitchers of varying types and arsenals, and it's probably the closest we can get to a stat which measures command. That said, the key here won't be reaching a target number, so much as showing improvement. Here are some prospects who really needed that improvement, and just how much they've achieved so far.

JOSE ALVAREZ -- LHP, Triple-A Toledo

Jose Alvarez was picked up to be Toledo rotation filler who had a slight chance to play his way into a greater role. His minor league history was no reason to be optimistic, and good prospects aren't typically cut at the AA level by the Miami Marlins of all teams. K/BB rate showed one of the reasons: in 2010, Alvarez was in A ball with a very nice 3.53 rate. That number declined steadily at his next two stops: 2.88 in 2011 between A+ and AA, and 2.69 in AA in 2012. A 2.69 K/BB rate is ok for a certain type of pitcher--namely, flamethrowing relievers and other big-armed prospects trying to find some command. Alvarez is a command and control lefty light on velocity. 2.69 is cut-worthy when the accompanying K-rate is 4.6, and so Alvarez had a tall order ahead of him. This year, he's been just as good at staying in the zone, but he's pitched much, much better inside the zone. He's nearly doubled his K/BB rate to 5.33 this year. The impressive leap is the main reason why Alvarez has gone from filler to fringe prospect in only 8 starts.

CASEY CROSBY -- LHP, Triple-A Toledo

Crosby represents the different kind of pitcher--the big-armed guy who only needs to his ratio to get around 2 before MLB teams take interest. After all, his ratio wasn't great last season when the Tigers called on him to make a few MLB starts. Crosby has had a long six years in the Tigers system. In 2009, a K/BB of 2.44 in West Michigan had prospect watchers drooling. Missing almost 2010 made his 2011 numbers relatively unimportant in the grand scheme. As one would expect, Crosby was bad in 2011, with a 1.57 K/BB in 25 starts with Erie. Durability and improvement were key as he rebuilt his prospect status, and last year was so far, so good. Casey Crosby made 25 starts in 2012 for the second straight season, and he posted a 1.72 K/BB despite jumping to the next level. This was encouraging until basically the minute Toledo's season began. Crosby has regressed at the worst possible point in his career; his K/BB now sits at 1.39, and all that's left is to wonder when he moves to the pen.

DREW VERHAGEN -- RHP, Advanced-A Lakeland

Drew VerHagen has not been playing minor league ball very long. The Tigers' 4th round pick out of Vanderbilt, the 6'6" righty features a three-pitch array and a fastball with nice velo and life. You always want to see guys like this make it as a starter, and that role is often determined by a guy's ability to post solid ratios as a starter early in his career. VerHagen pitched only 31 innings in 2012, with a K/BB ratio of 1.36, certainly not good, but in far too small a sample to be relevant. The real test for Drew will be in his 2013 assignment to Lakeland, where he's been given the chance to show his starter potential. So far so good; VerHagen is posting a K/BB rate of 2. He's shown good control of the strike zone, a foundation on which he can build better command, learn to strike more guys out, and make future improvements. Further improvement this season could cement him as a top 10 prospect and create real buzz as he gets an eventual promotion to Erie.

MONTREAL ROBERTSON -- RHP, Single-A West Michigan

Much like VerHagen, Montreal Robertson is a recent draft pick with enough of an arsenal to be cast as a starter, but not enough stuff to be cemented in the role. The 29th round pick in 2011 from Coahoma CC, Robertson hasn't done all that much pitching, tallying 111.2 innings across three seasons. In 2011, he worked almost exclusively as a GCL reliever, and in 2011 he made nine starts and two relief appearances for short-season Connecticut. None of these samples are large enough to mean a whole lot, but he really hasn't shown much command of anything in his career. In 2011, his K/BB rate was at 1.38. In 2012, it improved to 1.65. Now, it sits at an abysmal 0.95 in seven starts for the Whitecaps. I hate to be judgmental of such small samples, but that's a terrible number for a soon-to-be 23 year old pitching in Single-A ball. If nothing else, his age dictates that the Tigers will need to decide his role quite soon. Robertson's lack of control or command will make that an easy decision if he doesn't show immediate improvement.