Texas Rangers' starter Yovani Gallardo is having a great month of June. After his 8.1-inning shutout start against the Toronto Blue Jays on Saturday, the former Brewer is in the midst of a 23-inning scoreless streak.

Overall, his performance in 2015 has been one of the things keeping the Rangers surprisingly competitive. Acquired in the off-season from the Brewers in the last year of his contract, Gallardo was considered a serviceable mid-rotation starter whose value had taken a bit of a hit from its peak in 2010-2011. During that peak, he struck out 24.4 percent of batters he faced, good for 6th in all of baseball.

Gallardo's repertoire featured four-seam fastball, slider, and curve (with the occasional change-up thrown in), and while never quite an ace, was a very good strikeout pitcher during this time (3.32 FIP). However, as years passed, his fastball velocity has fallen, and with it, so have the strike outs (data from Brooks Baseball and Fangraphs).

Season vFB K% BB% GB% FB% 2010 93.3 24.90% 9.30% 43.00% 33.00% 2011 93.5 23.90% 6.80% 46.60% 36.50% 2012 92.5 23.70% 9.40% 47.70% 31.50% 2013 91.6 18.60% 8.50% 49.20% 27.60% 2014 92.2 17.90% 6.60% 50.80% 29.00% 2015 91.9 18.10% 7.10% 53.10% 28.80%

While Gallardo has never had a truly bad season (his "worst" full season was a 1.8 fWAR 2014), FIP and ERA have been declining each season, and he appeared on the down slope of his career.

However, this season's relative success highlights an interesting evolution in the chart above. Beginning with his career-low rate in 2010, Yovani Gallardo has managed to increase his ground ball rate every season. In fact, his 53.1 percent rate in 2015 is currently tied for 15th among 98 qualifying starting pitchers.

This season, batters are making much more contact (71.1 percent) against pitches thrown outside the strike zone than his career average rate (61.9 percent). Potentially weaker contact generated in this way could explain some of the 2015 bump in ground balls.

This doesn't explain the multi-year trend, however. Changes in Gallardo's repertoire might better explain the total trend.

The usage rate of each type of pitch have clear trajectories, year-to-year. The ground ball-oriented sinker, introduced to his repertoire in 2011, is the most obvious change and features a sharp increase in use until arriving at its present rate.

With the decline in velocity, Gallardo has very fundamentally changed his usage of the four-seam fastball. As it generated fewer swings-and-misses, it became more frequently replaced by this new sinker. The curve ball has slightly declined in reliance over time, and lefties see the change-up with a slightly higher frequency.

One more notable change is steady increase in slider usage in every season from 2008-2015. Despite his fastball velocity drop, Gallardo is actually throwing a harder slider than ever before. What began as an 83.3 MPH pitch during his rookie season is now an 88.8 MPH offering, and is ranked by Fangraphs as the third-fastest slider in baseball. With a 10.2 percent whiff rate, it is also the pitch by which he most frequently misses bats.

By Brooks Baseball calculations, Gallardo's infrequently-used change-up is generating a high 20.4 percent ground ball rate, a career high for the pitch. He has interestingly managed to add more horizontal movement on the pitch basically every year of its use (he only made four starts in 2008). In 2007, the pitch averaged -3.1 inches of horizontal movement; in 2015 to-date, it has averaged -7.9 inches.

His sinker is generating a normal rate of ground balls, it is just being used more frequently.

It certainly appears that Yovani Gallardo has managed a transformation many pitchers only talk about accomplishing. While losing velocity, Gallardo added a sinker to his repertoire, pulled away from his four-seam fastball, and relied on a harder slider to generate his swing-and-misses instead. Despite having the lowest strike-out rate of his career, Gallardo is thriving due to a higher ground ball rate and a healthy willingness to adapt.

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Spencer Bingol is a contributor at Beyond the Box Score. You can follow him on Twitter at @SpencerBingol.