Article: Is Bo Bichette No Longer a Lefty Masher?

[Bob Ritchie]

On Wednesday, May 21, Will Harris posted a table on Bluesky that showed Bo Bichette had the lowest OPS (.434 as of May 21) among batters with at least 100 plate appearances against left-handed pitchers since 2024. Considering that before the 2024 season, Bichette posted a career .908 OPS and 147 wRC+ against left-handed pitchers, the .434 OPS was surprising. Why has Bichette’s performance against lefties lagged behind his pre-2024 record? Let’s take a look.‬‬‬

For context, in 2024, 27% of all plate appearances occurred when a hitter faced a lefty. Therefore, it is more important that a full-time position player perform well against righties than lefties. Nonetheless, Bichette’s OPS against left-handed pitchers is well below MLB’s comparable 2024-2025 average of .718 OPS. His underperformance is a red flag.

I included Bichette’s performance against right-handed pitchers for the analysis because it may offer some insights regarding his numbers facing lefties. Additionally, this study focuses on expected metrics (for example, xSLG) because these statistics eliminate the impact of defence (good or bad) that may distort how well or poorly Bichette has batted.

Table 1 shows Bichette’s performance by pitcher handedness. Concerning his metrics when facing right-handed pitchers, except for xISO, Bichette’s 2025 x-stats are superior to his pre-2024 numbers. The difference between the 2025 xISO and the 2019-2023 mark is insignificant. Furthermore, every 2025 x-stat exceeds the relevant box score number (xBA exceeds BA, xSLG exceeds SLG, etc.). Hence, against righties, Bichette is hitting very well this season. Also, Bichette’s batting in 2024 was poor because of injuries and other factors.

Regarding performance versus left-handers, my focus is on the 2024-2025 period because the 2025 sample is small (37 plate appearances). Also, the genesis of this article was the .434 OPS against lefthanders since 2024. I used the 2025 data vis-à-vis right-handers because the sample size was sufficient (188 plate appearances).

Concerning Bichette’s 2024-2025 batting metrics against lefties, three noteworthy reasons exist for the underperformance: bad luck, poor plate discipline, and difficulty hitting all pitch types, particularly off-speed and breaking pitches.

Bad Luck
When facing left-handers, Bichette’s 2024-2025 x-stats, as depicted in Table 1, considerably exceed the relevant box score metric. Furthermore, his 2024-2025 xOPS is .732, much better than the highlighted .434 OPS (.421 OPS as of May 27). Therefore, part of the reason why Bichette’s OPS against left-handers is underwhelming is bad luck. We should expect his 2025 box score performance against lefties to improve due to positive regression.

Plate Discipline
Table 2 shows Bichette’s plate discipline versus left-handers and right-handers. Table 3 depicts plate discipline by pitch type and pitcher handedness.

My observations are as follows:

• Compared to the pre-2024 period, the 2024-2025 Bichette is chasing at a higher rate when facing left-handers but making contact at a lower rate.
• His In-Zone Swing% is similar to 2019-2023 Bichette, but his In-Zone Contact% is higher.
• Bichette’s chase and in-zone contact rates on non-fastballs have markedly declined since 2024.

Performance by Pitch Types
Table 4 shows pitch mix and Whiff% data by pitcher handedness. Tables 5 and 6 depict Bichette's performance against fastballs and non-fastballs, respectively.

Concerning pitch mix offered by right-handers, there has been little change in 2025 compared to previous periods. However, against left-handers, Bichette has faced a higher allocation of fastballs in 2024-2025 compared to 2019-2023.

Fastballs
Bichette’s fastball performance against lefties during 2024-2025 lags behind 2019-2023. However, his 2025 x-stat performance against right-handed pitchers' fastballs is better than the 2024-2025 and 2019-2023 periods. Also, concerning fastball performance against left-handers, his 2024-2025 xOBP and xwOBA marks are lower than the 2019-2023 marks because his 2019-2023 11.2 BB% exceeds his 2024-2025 4.1 BB%.

Accordingly, Bichette’s underperformance on fastballs when facing left-handers is not a concern because his performance versus righties demonstrates that he can handle fastballs. Additionally, I expect Bichette’s walk rate to normalize going forward.

Off-Speed and Breaking Pitches
Bichette’s 2025 x-stats on non-fastballs versus right-handers are similar to 2019-2023. Therefore, as I noted in respect of fastball performance when facing right-handers, this season’s Bichette can hit off-speed and breaking pitches thrown by righties. The question is why Bichette has struggled to hit off-speed and breaking pitches offered by lefties.

One possibility is that, against lefties, Bichette is hunting fastballs more in 2024-2025 than in 2019-2023. The supporting evidence is as follows:

• Compared to 2019-2023, 2024-2025 Bichette has a higher fastball Chase% (35.8% versus 28.8%).
• His 2024-2025 fastball Swing% (all zones) is 60.5%, higher than 2019-2023’s 56.6% Swing%.
• The left-hander/right-hander fastball In-Zone Swing% spread has increased since 2024. The spread increased from 6.4 percentage points (80.5% less 74.1%) to 8.2 (78.2% less 70.0%). Put another way, compared to 2019-2023, Bichette’s 2024-2025 In-Zone Swing% versus lefties has declined less than his comparable rate against righties.
• Bichette's fastball 2024-2025 In-Zone Contact% jumped from 84.4% in 2019-2023 to 96.5%. Look fastball, see fastball, hit fastball.
• Since 2024, 69% of the pitches offered to him by left-handed pitchers are fastballs, up from 57% in 2019-2023. In other words, if Bichette is seeing a lot more fastballs, it makes sense to look for fastballs.

Therefore, if a batter is hunting fastballs, we should expect lower contact rates on non-fastballs because the batter is fooled more often due to the slower speed and more movement on off-speed and breaking pitches. The data support this expectation. When facing left-handed pitchers, Bichette's 2019-2023 non-fastball Chase Contact% dropped from 61.7% to 45.2%, and his In-Zone Contact% declined from 87.7% to 80.0% in 2024-2025. Also, when a pitch fools a batter, weaker contact should occur. And it does! Bichette’s 2024-2025 .245 xSLG is less than half of 2019-2023’s .525 xSLG.

In summary, if my hunting-more-fastballs theory is correct, Bichette’s performance against left-handers has suffered. He is making contact on non-fastballs at a lower rate, and his contact is weaker. It would appear that a more balanced pitch-selection approach may put Bichette back on the lefty masher path.

The Last Word
Since 2024, Bichette has struggled against left-handed pitchers. His OPS is well below the mark he posted before 2024. There are three reasons why Bichette’s performance against lefties lags behind the 2019-2023 period, namely bad luck, less discipline, and, it would appear, hunting fastballs at a higher rate than before. With the helpful hand of Lady Luck, better plate discipline, and less fastball hunting, Bichette’s performance when facing left-handed pitchers should return to his pre-2024 level.   

View full article

[M.E.]

Can we just say unclutch like the rest of these bums

[M.E.]

5 hours ago, M.E. said:

Can we just say unclutch like the rest of these bums

glad to be wrong today 

[Brownie19]

I can't say I hate the thought that Bo is hunting the fastball more.  I hope he maintains that approach and makes the necessary adjustments to start mashing LH pitching again.

He certainly turned on a fastball tonight - thankfully.

[John_Havok]

1 hour ago, Brownie19 said:

I can't say I hate the thought that Bo is hunting the fastball more.  I hope he maintains that approach and makes the necessary adjustments to start mashing LH pitching again.

He certainly turned on a fastball tonight - thankfully.

HR was off a changeup, but the remainder of your point stands

[Brownie19]

7 hours ago, John_Havok said:

HR was off a changeup, but the remainder of your point stands

FFS. I watched it on my phone.  Blah - but yes!

[Bob Ritchie]

10 hours ago, M.E. said:

glad to be wrong today 

Bichette has performed well with RISP and in high-leverage situations this season.  The MLB Average OPS with RISP is 0.723. In high-leverage situations, the MLB Average OPS is 0.693.

Below are Toronto's batting metrics with RISP and in high-leverage situations before last night's game. The RISP table is first.