Kyle Gibson is just a number four starter – and that’s okay

Kyle Gibson has been good for the Phillies so far, just perhaps not as good as you think.

Earlier this week, NBC Sports Philadelphia published an article by Corey Seidman about Kyle Gibson, entitled “In a month of peaks and valleys, one constant for the Phillies has been the new guy.” It was a timely article, coming the morning after Gibson confused Padres hitters over eight innings en route to a 7-4 Phillies win.

I have to disagree with the word “constant”, since Kyle Gibson was pretty awful on August 11 in Los Angeles (4.1 IP, 6 ER, 3 BB, 3 K, 1 HR). Seidman tried to side-step this by only looking at Gibson’s “starts” (his appearance on 08/11 was technically a relief appearance), but that feels a bit like cherry-picking to me. Perhaps coming in for the third inning messed with Gibson’s timing, but that’s pure speculation. I’d rather use the extra 4.1 innings of data to develop an opinion of Gibson than speculate about possible excuses. Besides, the Dodgers are the only formidable offense that Gibson has actually faced, so this data is pretty important. His other opponents (PIT, NYM, ARI, SDP) all ranked in the bottom five in the NL in runs scored over the past month heading into last Sunday’s game, and towards the bottom in nearly every other offensive category, too.

For the most part, however, I do understand the general point that Seidman was trying to make, and he isn’t wrong. Kyle Gibson has given the Phillies a legitimate chance to win in 4 out of the 5 games he has pitched. That’s exactly the kind of pitching the Phillies desperately needed more of during the first half of the season. Out of 50 qualified MLB pitchers, only 10 are averaging 6 IP per start this season, and Gibson is one of them.

However, I want to caution Phillies fans against getting too excited about Kyle Gibson, because he hasn’t been as good in Philadelphia as his four quality starts would have you believe. In his 5 appearances with the Phillies, Kyle Gibson is averaging over 6 IP per game. He has a 3.77 ERA. That’s impressive, no doubt. But pretty much any major league pitcher can string together four quality starts (especially if they’re allowed to have one disastrous ‘relief’ appearance in between). Need I remind anyone of when Vince Velasquez put up a 2.20 ERA in 32.2 IP from April 23 to May 25 and plenty of people thought he had finally become a reliable starting pitcher?

Photo by Ralph Freso/Getty Images

As was the case with Velasquez earlier this year, when you look past innings pitched and earned run average, Kyle Gibson’s numbers don’t look so pretty. Since the trade deadline, 33 National League pitchers have thrown enough innings to qualify for the ERA title. Of those 33, Gibson’s 3.77 ERA ranks in the middle-of-the-pack (21st) and his 31 innings pitched puts him in the upper third (9th). His 4.04 FIP is just a little worse, ranking 24th. His 4.92 xFIP is where it starts to look disastrous – it ranks 31st out of 33. His 5.08 SIERA is even worse, ranking 32nd. His strikeout to walk ratio (1.58) also ranks 32nd.

Since joining the Phillies, Gibson’s expected wOBA has been above league average, and in his last 100 PA it is .327, which translates to a 4.63 expected ERA.

Some people might argue that because Gibson is a ground ball pitcher, these advanced metrics (which often favor strikeout pitchers) aren’t as representative of his true talent. However, Kyle Gibson has not been known to out-perform his FIP, xFIP, or SIERA in the past. His xERA and K/BB ratio have also correlated quite strongly with his ERA over his career.

His saving grace has been his minuscule home run of 0.58 HR/9. He’s managed to do so thanks to a minuscule home run to fly ball ration of 6.7%. League average during that time period is 13% and Gibson’s career average is 14.1% (and 16.4% in August). This is why Gibson’s ERA (3.77) and FIP (4.04) look so much better than his xFIP (4.92).

Eventually, Kyle Gibson’s HR/FB is going to regress and he’s going to start giving up more home runs. Furthermore, Gibson typically gives up more home runs as the season goes on (he has given up 20% more homers in the second half than the first half in his career), and Citizen’s Bank Park allows more home runs than either the Twins stadium or the Rangers stadium where Gibson used to pitch.

The other two key stats to look at to tell if a pitcher has been lucky are BABIP and left on-base percentage. Gibson’s BABIP with the Phillies is .276 and his LOB% is 74%. Prior to this season, his career averages were a .308 BABIP and a 70.6 LOB%. Unfortunately, there isn’t much reason to believe Gibson can sustain a BABIP or LOB% significantly better than his career averages. His batted ball stats (ex. HardHit%, GB%, FB%, etc.) all look similar to his career averages, and he’s actually been striking out batters at a very low rate (5.52 K/9) since joining the Phillies. Plus, he pitched in front of a strong defense when he was in Texas, and now he’s pitching in front of the Phillies defense.

Sooner or later, Kyle Gibson is going to start letting more runners get on base and more of those runners are going to score. As that happens, his ERA will go up and his innings pitched per start will go down.

Five appearances and 31 innings pitched is a very small sample size to be sure, but my point is not to say that we should base our opinions of Gibson off of solely these five games. I’m simply providing a counterpoint to some of the many articles I’ve read that have praised Gibson’s performance over the past month.

Going forward, Kyle Gibson might be more of a 5 to 6 inning pitcher with an ERA in the mid 4s rather than a 6+ inning pitcher with an ERA in the mid 3s. And would be just fine. I want to stress that I’m not trying to trash Kyle Gibson here. He seems like a good pitcher and a good person, too. A number four starter is the kind of pitcher Gibson has been throughout his career, and it’s exactly the kind of pitcher we thought we were getting when the Phillies traded for him, and the fact that he’s pitched better than that over his first month in Philadelphia is just an added bonus. Most importantly, Gibson is certainly a heck of a lot better than Vince Velasquez, Matt Moore, or Chase Anderson.

Kyle Gibson probably won’t pitch at this level for the rest of the season, nor should we expect him to. On the other hand, given the current state of the Phillies offense and defense, Gibson might just have to stay dominant if the Phillies want any chance of reaching the postseason.

*All statistics as of 08/27/2021.