Can Mariano Rivera Delay the Inevitable?

It doesn't take a genius to figure out Mariano Rivera's performance has dipped a bit over the past couple of years. He's still effective, but he's hardly as dominant as he was during the Yankees' championship runs, even with an impressive strikeout-to-walk ratio. So, what's wrong with Mo? More than a slight decrease in velocity, Rivera is simply having trouble putting hitters away, specifically getting that all-important swing-and-a-miss. Batters, it seems, are making contact with Mo's cutter and four-seamer with more regularity. To wit: last night, it took Mo 10 pitches to retire Elijah Dukes, who fouled off four consecutive pitches (three cutters and one four-seamer) before grounding out to Robinson Cano. Already, in 27.2 innings, Mo has yielded 27 hits, only 14 less than he gave up all last year. Are we watching the beginning of the end for Mo?

Fangraphs illuminates this disturbing, possibly irreversible, trend. 

Move forward to 2009 and how has Rivera done? Well, noticeably worse is easy to see, but there are some frightening numbers beneath the surface. Rivera's 7.5% swinging strike rate is the lowest on record for him. There has been a sizable dip in the number of pitches thrown within the strike zone and hitters are not chasing these extra balls out of the zone.

Rivera’s ground ball rate is also at its lowest point on record, though that is over a smaller sample than his individual pitch results. It is no surprise then that the home run rate has increased, though the rate by which is has increased is surprising and not likely to continue. Rivera has allowed five home runs already this season through 26.2 innings. The last time he allowed more than five home runs was 1995 when he was a starter.

Interestingly, Rivera’s strikeout and walk rates have not moved much despite the drastic change in his individual pitch outcomes. 32 strikeouts to just two unintentional walks, and no hit batters, gives Rivera an even better ratio than last year. Given his extreme drop in missed bats and overall strikes thrown however, I would not expect that to continue. It will be interesting to see which regression, the strikeout and walk rates or the home run rate, influences Rivera’s final line the most.

I still have faith in Mo. Hell, I'd take him over 99 percent of the league's other closers. Given his age, however, I also have to admit that even the mighty Mariano is going to have to call it quits sometime. Hopefully, he can make some adjustments and deliver a few more postseason runs before he heads off to Cooperstown. 

(UPDATE:) RAB counters. I'm not sure who's right, but it's interesting that the same data can lead to two different conclusions. Half-empty, Half-full, I guess. At least we can agree there's still a glass.