Collin McHugh and the curious case of his sweeper

Apr 10, 2023

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Collin McHugh has a good ERA for the Atlanta Braves, but signs point to serious regression.

Collin McHugh was a steady, reliable arm for the Atlanta Braves bullpen in 2022, following his exceptional year for the Rays in the 2021 season.

Even though he has a respectable ERA of 3.18 (which, when adjusted is 41.0 percent better than average), almost everything else for McHugh points to him being extremely fortunate so far this season.

Even though his ERA is 3.18, his expected ERA (xERA) is 5.06, and there are a lot of factors that are going into this.

His strikeout rate of 13.6 percent is the lowest of his career and ranks him in the bottom 5.0 percent of the league. This is a huge drop-off from his 27.6 last year. Combine this with his 9.7 percent walk being the highest of his career, and you can see how there are going to be problems. In fact, his walk rate is almost double his 5.1 percent of last season.

McHugh is also struggling with giving up hits. His 11.9 hits per nine innings and his WHIP of 1.765 are his worst since 2013 when he pitched 19.0 of his 26.0 innings for the Rockies.

When you look at his hard-hit percentage, it is no shocker that he is giving up so many hits. His 36.4 percent is his worst since the stat was tracked (2015). He used to be elite in this category. In his previous three seasons he was in the top 9.0, 4.0, and 8.0 percent of the league in preventing hard hits respectively. This season, he is still decent at top 37.0 percent, but it is a huge drop-off.

So far, we have seen that he is giving up hard hit balls more often, giving up more hits, walking more batters, and striking out fewer batters. So, what gives? What is causing these drop-offs?

What is going on with Collin McHugh?

Over his career, McHugh has used a wide variety of pitches. Since 2015 he has had seven different pitches in his arsenal. However, since the start of 2022, he has relied heavily on his sweeper and cutter.

In 2022 he used his cutter 47.5 percent of the time, and his sweeper 48.3 percent of the time. He would occasionally throw a curve (3.4 percent), or a 4-seamer (0.8 percent).

In 2023, it has been more of the same with is 4-seamer used slightly more. The Sweeper has been used 47.3 percent, cutter 45.5 percent, 4-seamer 4.7 percent, and curve 2.5 percent.

At first glance we can see that hitters are hitting his most used pitch (sweeper) harder on average, hence the decrease in preventing hard hit percentage. Currently, hitters are hitting his sweeper almost 4 MPH harder on average than last year. If we look at the last three seasons, hitters were hitting his sweeper at 85.2, 85.5, and 89.3 MPH respectively.

Last season, hitters had a batting average of .150, xBA of .162, slugging percentage of .242, and xSLG of .247. This season they have a .278 batting average, xBA of .244, slugging percentage of .370, and xSLG of .430.

Hitters are also swinging and missing at his sweeper the least they ever have. As you can see on the below chart (even though it is crazy with all the different pitches), that in 2017 was his best rate at 39.8. This season his rate is a career worst 28.7.

This could be partly because hitters are seeing his sweeper better, but he is also only throwing it inside the strike zone only 39.5 percent of the time. Remember, this is his most used pitch. This is the second lowest rate of his career with this pitch. To be fair, it was slightly lower last season, so this is not the main issue, just a piece of the pie.

Hitters seem to recognize this and are not chasing the pitch outside of the zone nearly as often. His 28.7 percent chase rate on his sweeper is the lowest of his career and is a significant drop from 36.5 percent last season. We can also see a similar story on his cutter in the chart below.

What is interesting is that his sweeper has more movement than last season. This season his sweeper has had 0.2 inches vs average in horizontal movement in comparison to 0.1 last season. With vertical movement it went from 1.6 inches vs average to 1.9 this year. Of course, "vs average" compares to other like pitch types across the league. If we look at pure movement vertically his sweeper has increased from 42.6 inches of drop to 43.3. Horizontally it has decreased from 16.4 inches to 16.0.

These changes don't scream red flag.

His velocity on the pitch has dropped from 80.2 MPH in 2022 to 79.6 this season, but it was 79.5 MPH in 2021 and he had success with the pitch. Hitters had a batting average of .177 and a slugging of .262 in 2021. So, again, no red flags there.

What appears to be the case is that hitters have just learned to lay off the sweeper outside the zone and wait on pitches that are in the zone, resulting in more quality contact. His barrel percentage has sky-rocketed against this pitch. His 9.5 percent is almost double last season (5.5 percent) , and over triple what it was in 2021 (2.2 percent).

You can also see that the barrel rate against his cutter is way down, which tracks because his hard-hit percentage of 33.3 percent is his best since 2018.

In summary

To keep it fair, McHugh has been good so far in keeping runs off the board, which is ultimately his job.

However, a lot of variables show that if he does not make adjustments soon, there is a high probability that runs will be scored at a higher rate.

With his WHIP, strikeout rate, and walk rate being really bad in comparison to what we are used to seeing from him, it is only a matter of time.

It seems to stem from his most used pitch, the sweeper, being less effective this year than it has been in the past. Hitters seem to have figured out that he does not throw it in the zone very often and have been able to wait on one they can actually hit, and then hit it with better quality contact than they ever have in McHugh's career.

Hopefully McHugh can continue to keep runs off the board while figuring out the adjustments he needs to make on his sweeper to get it back to one of the better pitches in the league.