Numbers to Watch During the Second Half

The second half of the 2021 season is now upon us with the All-Star Game — and those hideous uniforms — firmly behind us in the rearview mirror. Technically speaking, the Astros are actually nine games into the second half, but the Mid-Summer Classic is traditionally considered the half-season marker. Although my brain fights strongly against that arbitrary cutoff point for a 162-game season, I’ll roll with it for simplicity's sake.

With a 55-36 record in their first 91 games, the Astros are considered one of the best teams in the season’s first half. They’re currently 3 ¹⁄₂ games ahead of the second-place A’s in the AL West, with a 96.2 percent chance to qualify for the postseason. For the division, Houston also sports an 87.1 percent chance to take the title for the fourth time in the five seasons. Not a bad place to be at this point of the year.

To say that the first half has been smoothing sailing for the Astros would be a fabrication. For one, this club has had to overcome plenty of injuries to get to this point of the season. Not having Framber Valdez and Jake Odorizzi at the start of the campaign did place an early strain on the pitching staff. The bullpen has also struggled with a lack of quality options in the depth chart. The lineup, however, has been the one true constant for this team despite some injuries and COVID-related absences. These factors are primarily why we’ve seen Houston have that mid-April swoon in addition to a couple of difficult stretches. But when this team catches fire, there is little external opposition that can stop them.

One of my favorite projects during the season is to track various metrics for individuals and clubs. While a club’s record matters for obvious reasons, it also helps to understand how, for lack of a better term, how the sausage is made. Or, you know, what makes the engine rev up or stop cold. Below are some of my favorite stats to look up for each of the three units this season (position players, relievers, and starters), and I hope you find these useful as well.

Contact and Strikeout Rates - Lineup Edition

Death by a thousand cuts is probably an apt way of describing the Astros’ offense to an opposing pitcher. They don’t strike out often at 19 percent — the lowest mark in Major League Baseball — while maintaining the highest contact rate at 81 percent. The difference between Houston’s rate and the second-place club — the Angels at 77.4 percent — is roughly the same as Anaheim Los Angeles to the 27th-place club in Milwaukee. That is honestly remarkable in today’s baseball.

While contact rate isn’t everything, as evidence by last year’s performance with a power outage issue, the Astros are at their best as an offense by putting constant pressure on the pitcher. By not striking out often and putting the ball in play, it is only a matter of time before good things happen. Both of these rates provide a valuable snapshot into how this lineup is performing under the hood that I refer back to often in a season.

Walk Rate - Bullpen Edition

One of my soapboxes last season was that the bullpen was suspect, largely due to this unit’s propensity to issue plenty of walks. For as much as I believe that the metrics from 2020 are generally useless, it was concerning how only the Mets at 12.6 percent had a higher walk rate from their relief corps than the Astros at 12.4 percent.

Walks, as you know, can kill a pitcher. Not literally, yes, but you get the point. Thankfully, we’ve seen the bullpen settle around the middle of the pack in terms of walk rate at only 10.4 percent. This unit, for better or worse, is about average in terms of overall performance right now. With reinforcements likely on the way from the IL and possibly an addition at the trade deadline, the bullpen could look better in the season’s second half. But watch that walk rate as it could portend to a swing in this unit’s overall performance.

Left on Base Percentage and Home Run to Fly Ball Ratio - Rotation Edition

The Astros’ starting rotation thus far has been one of the best about limiting damage. This is indicated with a left on base rate (LOB%) of 78 percent, trailing the Dodgers at 80.6 percent. For context, the league-average LOB% for all starters in 2021 is 72.8 percent. As noted here by FanGraphs, the rate isn’t the traditional measure of left on base numbers that we see in a box score. Instead, this rate is calculated with the formula below.

LOB% = (H+BB+HBP-R)/(H+BB+HBP-(1.4*HR))

The interesting aspect about the Astros’ rate this season is that the rotation is roughly middle of the pack in both strikeout and walk rates. Normally, a club — or pitcher — with a higher strikeout rate may post a higher LOB%. The Dodgers, for example, lead Major League Baseball with a 29.1 percent strikeout rate compared to the Astros at 23.7 percent. In other words, Los Angeles can pitch itself out of jams. So, how does Houston maintain that low of a LOB% if they’re middle of the pack in strikeouts and walks? The answer is that they currently own one of the lowest home run to fly ball ratios (HR/FB) at 12 percent. As long as the ball stays in the park, Houston’s starters can limit the damage. If not, then that could become an ugly issue later in the season.