In 2009 Matt Capps had a year which no one, not even him, could figure out.
His strikeout rate, 7.62 K/9, was the highest of his career. His groundball percentage, 40.7, was the highest it had ever been, and his average fastball speed. 93.6 MPH, was the highest of his career. Yet for some reason, Capps couldn't manage to effectively get batters out at the rate he had the two seasons before. Despite finishing with a career high 27 saves, Capps ERA ballooned from 3.02 in 2008 to 5.80 in 2009. His walk percentage rose to the highest of his career, 2.82 BB/9, and he allowed 10 home runs in 2009, five more than in 2008.
It just didn't make sense, he had a career high ground ball percentage, yet an incredibly high BABIP at .370. He wasn't throwing more balls than in the past, yet he was walking more batters, and his fastball, which used to be one of the best pitches in the majors, was below replacement value in 2009 according to FanGraphs.
Regardless of the inexplicable problems of 2009, as many as 12 teams attempted to sign Capps in 2010. The Nationals landed him with a one-year $3.5 million contract. So far the results have been more than pleasant, with Capps converting all 13 save opportunities, striking out 8.35 batters per nine innings and posting an ERA of 0.98. In straightening out Capps, it seemed confidence is what worked.
While the outcome was good for Capps first five outings, the method was a little shaky. He recorded saves in four-out-of-five of those appearances and only allowed one earned run. Yet he was still doing the same bad things that got him in trouble in 2009. In that stretch he walked five batters, and allowed six hits. For Capps, going into the second half of April on a Nats team that had a winning record, and four saves with a low ERA under his belt, had to have helped him believe that he was back...even if some of the deeper signs of trouble were still there.
Since then he has struck out 13 batters in 12 appearances while only walking one. He's allowed only one earned run, earning him his only loss in a two-inning non-save situation. His season BABIP is back down to it's career average, .273, and he's striking people out at the best rate of his career, and his fastball is again rated as his best pitch according to FanGraphs.
While there is no way to empirically prove it, I believe that Capps failures last season came as a result of poor confidence in a failing situation. Capps knew he was entering the prime money making time of his career, yet he was floundering. The same pitch that made outs in the past were turning into home runs. He was throwing the same amount of balls and strikes as in the past, but he was badly misplacing the strikes resulting in hard hit balls instead of outs. It seems his early success in 2010 has helped straighten him out, and as a result, the Nats have the saves leader in the major leagues on the club.