We are not witnessing a Marcus Stroman breakout

As it stands, the Toronto Blue Jays season has been a bleak affair, made slightly better for the club by a couple of bright spots. The most obvious is Justin Smoak, but perhaps second on that list is Marcus Stroman.

Last year, Stroman proved that he could be a workhorse by logging 204 innings, but by the most traditional metrics he didn’t pitch up to his talent level. His 9-10 record and 4.37 ERA said “mid-rotation guy” not “ace”. In 2017, by contrast, he’s 10-6 with a tidy 3.00 ERA that suggests he’s taken the next step.

However, Stroman’s performance level this year is almost exactly identical to what he did last year. Looking at his basic peripherals, the differences are imperceptible.

Even looking at the batted ball data, there isn’t a meaningful distinction to be drawn between the seasons.

There has been a tiny uptick in groundballs and downturn in line drives for Stroman, but the overall results are exceedingly similar. When hitters put wood on his pitches nothing profoundly different is happening.

In terms of his stuff, there has been a small increase in fastball velocity and a move to throw more sliders and fewer cutters, but at the end of the day it’s hard to characterize those changes as particularly important when they don’t result in meaningfully different results in any category.

With the most important numbers remaining stationary, the pertinent question becomes what, exactly, is different. In this case, it’s Stroman’s success with runners on base. Traditionally speaking, the right-hander has performed significantly worse when pitching with men on. The difference during his first three MLB seasons looks like this:

It’s normal for a pitcher to perform slightly worse with runners on, but his particularly significant split helps explain why his ERA (3.91) is much higher than his FIP (3.38) over that time period. Because he struggled once the bases started to get full, his strand rate of 69.9 percent was pretty unimpressive for a pitcher of his calibre. For reference, the average in that category league-wide this year is 72.6 percent.

This season, the trend of Stroman scuffling out of the stretch has been turned on its head. He’s leaving a hefty 77.6 percent of runners on base, which just about single-handedly accounts for his increased ability to keep runs off the board. Contrary to the pattern of his career, in 2017 he’s been more successful with runners to contend with.

Theoretically, you could interpret these numbers as evidence that Stroman has put a problem from his early career behind him and is taking the next step. The right column of the chart shows why that would be a dubious takeaway.

Stroman has been more successful with runners on than off this year in terms of results, but he hasn’t actually pitched better. When men are on base he’s struck out far fewer batters and the reason he’s conceded a more modest slash line in that situation has far more to do with a low BABIP (.286 to .329 with the bases empty) than anything else. That hardly indicates he’s turned any kind of corner.

With all this information in mind, there’s still no disputing that Stroman is having a fine year. The 26-year-old is near the top of the league in innings pitched and Wins Above Replacement. It’s simply inaccurate to describe what he’s doing as any kind of breakout, because he’s not doing anything differently.

Because of a dearth of strong traditional numbers, the baseball world probably didn’t give Stroman enough credit for his 2016 performance. By the same token, he’s likely receiving more praise for his work on the mound this year than his performance merits, thanks to a turnaround in his record and ERA.

He’s significantly better than his 4.37 ERA from last year suggests and worse than the crisp 3.00 mark he’s sporting this season. The answer resides in the middle – as answers tend to do.

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