Enter … David Robertson?

Looks like a strike out to me.

I was crushed when I learned that . I found out about the injury under unusual circumstances. I got home late from work and didn’t watch the entirety of the Yankee game that night. I didn’t see any commentary. I turned the game on in the sixth and turned the TV off as soon as the game was over, making and eating dinner along the way. I was none the wiser about the injury until I was drinking my morning cup of coffee watching Sports Center. The news was shocking and saddening. It is a pleasure to watch Rivera pitch. It is also something I take for granted. The idea of the Yankee bullpen without Mo is like the idea of the Yankees without pinstripes. I know one day Rivera won’t be manning the late innings for the Yankees, but I remain unprepared for that day.

There is no question the Yankees are diminished without Rivera. Every team in baseball can use a reliever of his quality. I don’t care if the man is pitching the third inning. The Yankees are better with him. However, of all the key Yankees Rivera may be the one the team is most well equipped to replace. The bullpen is a source of real strength for the team. The Yankees have not one, but two, players ready to step in and fill Rivera’s role until he comes back next year (and you know he will).

With all due respect to , if the Yankees are going to insist on saving one of their best relievers for the ninth inning, as opposed to using him when the situation demands it, then that player should be . Robertson isn’t just the best healthy reliever on the Yankees. He’s the best healthy reliever in baseball.

Robertson is no secret to Yankee fans. He’s been a solid option in the bullpen ever since 2009, when he posted an ERA/FIP/xFIP split of 3.30/3.05/3.15. He struggled a bit in 2010, and then underwent a metamorphosis in 2011. Bluntly put, Robertson was masterful last season, putting up one of the best seasons I’ve ever seen from a reliever. His line was 1.08/1.84/2.46. He continued his history of racking up the strikeouts, fanning 13.5 batters per nine innings. He stranded an impossible 89.8% of the runners he inherited. That was dominance.

This season Robertson is picking up right where he left off. He’s given the Yankees just 12 innings so far and he’s allowed zero runs. More importantly, he’s not getting lucky. His ERA is 0.00, of course, but his FIP and xFIP are 0.21 and 1.12. Those are low numbers. Robertson’s signature is the strikeout. He’s currently striking out 15.75 per nine, on pace for a career high.

If Roberston has a weakness to his game it’s that he allows too many base runners. Last season, in between striking a ton of batters out, he issued 4.73 walks per nine innings, right in line with his numbers from 2009 and 2010. To put that high total into perspective, for a one inning reliever that average means David is handing out a free pass once out of every two appearances he makes. Given that he’s called upon to work in high leverage situations those walks are akin to playing with fire. Although he limits the damage with all those strikeouts, eventually those walks will come back to burn him.

Here’s the good news: so far this season Robertson has cut down on the walks tremendously. In 2012 he’s walking only 2.25 per nine innings. That, combined with the fact that he’s striking everybody out, means that he has a WHIP of just 0.83. That WHIP is Mariano territory. If Roberston can maintain something near it for the entire season he’ll provide the Yankees more than enough to fill in for Rivera.

David Robertson has been one of the less well sung heroes on the Yankees the past few seasons. He’s been a solid contributor out of the bullpen since 2009, but it is only in the past two seasons that he has emerged as one of the best relievers in the game. Over the first month of the 2012 season he has been, without question, the best reliever in the game. Having an asset like that is how the Yankees can overcome losing the best reliever in the history of the game.