Mike Pelfrey was a nice story early in this Twins season, when he provided an unexpected boost for the Twins while taking the place of Ervin Santana in the rotation following Santana's suspension.

That cute little story, however, has morphed into something even better for the Twins: Pelfrey woke up Monday morning with the fourth-best ERA among American League starters, a cool 2.28. Considering most fans would have been pleased with a number approaching double that figure, Pelfrey's work on the mound has been nothing short of a revelation. He threw eight shutout innings Sunday, snapping a two-game Twins losing streak and giving them an important home win. That brought Pelfrey to 28 innings pitched in his past four starts, with just three runs allowed total in that span.

The biggest question people have – considering they saw a post-Tommy John surgery Pelfrey wobble with a 5.19 ERA in his first year with the Twins in 2013, followed by a 7.99 ERA in limited action in 2014 – is how on earth this is happening? The two-year contract the Twins gave him after that 2013 season seemed like sunk cost. Instead, he's been brilliant. New results are usually the product of new approaches, and here are a few things Pelfrey has done differently this year, per an analysis of FanGraphs data:

*Split-fingered fastballs: As Pelfrey noted in this Jim Souhan column after Sunday's game, the split-finger fastball has become a major weapon for him this season.

Two things about the splitter are notable. First, Pelfrey is throwing more of them than he ever has at any point in his career. Per Pitch f/x data, he has thrown splitters 16.8 percent of the time; the most he has ever thrown in a full season was 15.9 percent in 2010, which was one of his best years in the majors (15 wins, 3.66 ERA with the Mets). As you can see by the chart below, he threw fewer splitters from 2011-14, though a couple of those season (2012 and 2014) were pretty short because of injury problems.

Also, Pelfrey is throwing the splitter at a slower speed. His average splitter velocity each of the past five seasons was somewhere between 84 and 86 mph. With a fastball that usually sits between 92 and 93 mph, that's not always a great difference between speeds – giving batters a better chance to adjust to the pitch. This year, however, Pelfrey is throwing the splitter an average of 81 mph, making it not just a pitch with movement but a true change-of-pace.

*Sinkers: Pelfrey is still throwing a healthy number of fastballs, but the vast majority of them are sinking fastballs this year. Pitch f/x has him at throwing sinking fastballs 53.8 percent of the time, whereas in 2013 – his only full year with the Twins – that number was 40.8 percent. The result has been seen in the types of contact batters are making. Pelfrey is getting ground balls 55.2 percent of the time – a pretty good jump from his overall career average of 48.1 percent.

It's helped Pelfrey avoid homers – just three allowed in 67 innings – while opponents are making "hard contact" just 19.9 percent of the time, far better than his career average of 26.4 percent.

*First-pitch strikes: His first-pitch strike percentage of 60.1 is not great, but it's much better than in his two previous seasons with the Twins (55.3 in 2013 and 49.6 last year). Any pitcher is better when working ahead in the count, and that's particularly true of Pelfrey – especially now that he has an "out" pitch with that improved split-fingered fastball that he's throwing with so much confidence.

Essentially, Pelfrey in recent less successful seasons was throwing like a power pitcher without the stuff of a power pitcher. He's adjusted his approach, and it's paid off. Whether Pelfrey can keep this up remains to be seen. For now, though, the results are real and the data shows they're not a fluke.