Early Red Flag For A's Rookie Mason Barnett?

Barnett began the year in Triple-A Las Vegas, and spent the majority of the season there, getting into 25 games (23 starts) and holding a 6.13 ERA (5.53 FIP) across 119 innings of work. His strikeout rate tanked, dropping to 22.8%, while his walk rate ballooned to 11.9%.

Still, it was his first year in Triple-A, and those types of struggles are expected from guys.

Then, as injuries mounted in the A's rotation, with both Jacob Lopez and Joey Estes landing on the IL just before September, Barnett was called up to The Show. This may have been partly because he was already on the 40-man roster and the Athletics didn't want to DFA anyone at that point in the season.

Was he rushed? Perhaps. But this was still a great opportunity for Barnett to gain some experience ahead of the offseason and get some first-hand knowledge from facing big-league batters. That can be extremely helpful for young players, as they get a better sense of what they need to work on over the winter.

Cause for Concern?

One stat jumped out to us once Barnett's final outing was in the books, and that was that his left-on-base rate sat at just 59.2%, albeit in 22 1/3 innings of work. While retiring a few extra batters wouldn't have had a huge impact on his 6.85 ERA in his first stint with the A's, it was something that seemed out of the norm.

Among qualified pitchers, the lowest LOB% in the big leagues belonged to Mitchell Parker of the Washington Nationals at 60.5%. Among pitchers with at least 20 innings of work, Barnett was far from the worst, but the common theme among the pitchers in this part of the leaderboard was that they underperformed their FIPs by a wide margin.

Barnett's FIP was 4.88, which would have been a whole lot better—presumably with a league average LOB%. On the bright side, this does seem to be a stat that is a little more volatile year-to-year, sort of like one-run wins on a team-wide level.

What's potentially worrisome for Barnett is that he has shown consistently in the minor leagues that he has run low LOB% too. With the Royals Double-A squad, it sat at 64.2% before shooting up to 79.7% in his seven breakout starts with the A's affiliate after the trade. In Triple-A this season, it also sat at 66.8%.

What Mark Kotsay Thinks

During the final week of the season, Mark Kotsay was asked about relief pitcher Hogan Harris, who had given up a home run in the ninth inning in Boston, but then had his hard-nosed mentality that got him the save at Fenway. Obviously starting and relieving are different animals, but perhaps there is a mental component to struggling to shut things down when there are runners on base.

So we asked Kotsay if in Barnett's case, it's something that could be mental, a small sample size thing, or if this is an early indicator that he needs a go-to out pitch.

"It's hard to assess young starters. You hear me say it all the time, [it takes] 20-30 starts really before I want to pass a legitimate judgement on whether they're capable of making the adjustments. I think he's capable of making the adjustments. We had a good conversation [in late September], just in terms of what he needs to do this offseason.

"Come back, be prepared to compete for an opportunity to be in this rotation."