Marco Estrada is a pitcher with both impressive strengths and serious limitations. As a result, he’s been a roughly average starter for the majority of his career.

His changeup is one of the best in the game. The pitch absolutely baffles hitters with a late tumble that seems to challenge the laws of physics. It has claimed many victims over the years and in his most recent gem Evan Longoria, Joey Butler and Curt Casali were the latest casualties.

On the other hand, Estrada’s fastball often lives below 90 mph without significant sinking action. He has to throw it for the changeup to be effective, but if he doesn’t hit his spots with the pitch he can get into serious trouble.

The end product of this repertoire is a pitcher who can make hitters look silly one minute and be hit all over the ballpark the next.

However, this year has been a different story for Estrada. Since joining the Toronto Blue Jays he has been excellent, posting a 3.45 ERA in 73 innings and dazzling in his last two starts, taking no-hit bids deep into both games while drawing comparisons to Dave Stieb.

Last season the right-hander posted an unimpressive 4.32 ERA and an even worse 4.88 FIP, so what has changed?

One of the first places to look when pitchers seem to be doing significantly better or worse than their track records is their pitch mix. Throwing a particular pitch more or less often, or even adding a new one to the arsenal can radically alter a pitcher’s fortunes.

In Estrada’s case, there really hasn’t been much change. According to Brooks Baseball he has increased his cutter usage at the expense of the four-seam fastball, but it’s far from a profound overhaul.

The next place to look for meaningful change is in peripheral statistics. Numbers like win-loss record and ERA show how a pitcher is contributing to the bottom line, but they have serious limitations.

When comparing Estrada’s peripherals this year to 2014 there is a very little difference, except for one very specific area.

Year K/9 BB/9 BB/K HR/9 HR/Fly Ball BABIP xFIP 2014 7.59 2.63 2.89 1.73 13.2% .257 4.19 2015 7.77 2.84 2.74 0.99 8.5% .243 4.19

In almost every way Estrada’s performance between the two years is very consistent. He has commanded the ball well and put up solid strikeout numbers while having very few balls in play land for hits.

There is really only one difference and that’s the home runs. A far lower percentage of Estrada’s fly balls are going over the fence this year, a piece of information that is very difficult to interpret.

Many consider home run/fly ball rate almost entirely luck-based, which is why the statistic xFIP exists. The metric regresses FIP to account for how many home runs a pitcher should be expected to give up based on his fly ball rate as opposed to how many he actually does.

Given that Estrada’s xFIP in 2014 and 2015 are exactly equal you could say that he was very unlucky with fly balls leaving the park last season and quite lucky this year and there’s no real difference in what he’s doing as a pitcher. That’s a defensible stance, but it’s narrow and probably incomplete.

While pitchers can’t control fly balls once they’re off the bat, they do have an influence on how hard those balls are hit. According to FanGraphs, Estrada has only allowed 23.3 percent hard-hit balls, the eighth-lowest number among pitchers with at least 70 innings pitched, right behind Chris Sale. His career average is 32.9 percent.

Specifically the fly balls he’s allowed can be tracked by both location and exit velocity off the bat and they look like this:

The lack of dark red here stands out and it’s apparent that Estrada has given up many relatively softly hit fly balls of medium depth. That’s a great kind of batted ball to induce because it almost always results in an out.

When the Blue Jays acquired Estrada from the Milwaukee Brewers in exchange for Adam Lind there was no expectation that he’d be one of their most reliable starters, but that’s where things stand now.

For him to sustain his success he will have to keep demonstrating the ability to keep fly balls in the park- a skill that is poorly understood at best and possibly more dumb luck than anything else.

Even so, last year Estrada led MLB in home runs allowed and this season he’s one of the most difficult pitchers in baseball to hit the ball hard off of. That seems like a pretty good start.