Cleveland set a number of records last year by means of a dominant collective pitching effort. This contributor noted last summer how the Indians’ rotation was distancing itself from the rest of baseball, and on Oct. 2, Jeff Sullivan argued that the Indians might have had the best overall staff of all time. They were the best of all time by some measures, including total WAR.

Then earlier this season, remarkably, the Houston Astros appeared set to better that Cleveland staff, recording an ERA that was almost 50% better than average over the season’s first two months.

But guess what? The Indians are making another run. And while the club’s overall staff (relievers included) might not ultimately rival Houston’s, the Indians’ rotation just might be able to chase down the Astros’.

Including yesterday’s games, Cleveland now ranks second second in the majors in starting pitching WAR (10.1), behind only the Astros (10.9). But over the last 30 days, the Indians are first by that same measure (5.1 WAR), and it’s not particularly close. As of Sunday, the Yankees ranked second (3.3) and the Red Sox third (3.0). The Astros? Only 16th (1.6).

While one could point to the benefit of playing in an extremely weak AL Central with an unbalanced schedule, the Indians’ starters are also really talented. They became the first rotation to strike out 10 batters per nine innings last season (10.08). And while the Astros threaten to break that mark (10.21) this season, Indians starters are averaging a staggering 11.09 strikeouts per nine over the the last month, best in baseball. That’s a 30.4% strikeout rate.

While a 30-day period is somewhat arbitrary, these start-and-end points are a little more meaningful for a specific reason: the Indians have enjoyed the emergence of another ace.

You’re aware of the talents of reigning AL Cy Young winner Corey Kluber and right-hander Carlos Carrasco. They remain very good. Mike Clevinger has built upon his 2017 breakout, as well. But with his 11-strikeout effort on Saturday, it was Trevor Bauer who not only led the Indians staff in pitching WAR (3.9) play Monday, but also all of the American League. Bauer has surpassed his previous best single-season WAR total of a year ago (3.6).

Over the last 30 days, Bauer leads all of the majors league starters in WAR (1.9), FIP (1.53), and strikeout percentage (39.6%). At the close of May last year, Bauer had the worst ERA in the majors in qualified starters (6.00). Thirteen months later he ought to be a sure-fire, first-time All-Star and finds himself in the American League Cy Young Award race.

Bauer’s improvement seems very real. Some of it is gradual. He’s improved this command and slashed his walk total each of the last three seasons. He’s also increased his fastball velocity in each of the last three seasons, and now the pitch is averaging 94.6 mph. But he’s throwing his fastball less than ever, as well. It was the fastball that was hit at times last year. Bauer can go away from the pitch because he has dramatically and effectively added to his arsenal.

While Bauer’s breakout started in the second half last season when he began to rely upon of the game’s best curveballs more often, he has since added a slider from scratch this winter, and has also improved and gained confidence in his changeup.

Consider this darting, perfectly placed example of the latter pitch from Saturday:

Batters are hitting just .102 against his slider and it ranks 14th per linear weights among all sliders, worth 8.6 runs above average. His slider, changeup, and curveball area all generating whiff-per-swing rates of 37% of better.

In short, Bauer has benefited from improvements across the board. Just as the Astros added another weapon in Gerrit Cole this offseason and created a new one in Charlie Morton the previous year, the Indians have essentially enjoyed the addition of another frontline pitcher in Bauer.

The result is that a club featuring one of the league’s top rotations has maybe somehow improved. Four of the team’s starting pitchers appear among the top 12 in AL pitching WAR. Shane Bieber, meanwhile, has allowed less than three runs per start on average in his first three major-league appearances.

The Indians still have issues in the bullpen, though Neil Ramirez and Oliver Perez have helped. It’s unclear what they will do in center field; Roberto Perez is also really struggling with his bat (33 wRC+) as the No. 2 catcher. Still, come October, you want to begin with an elite rotation. The Indians appear to have one. The Astros have neither won the AL crown, nor earned the title of best-ever staff, just yet.