It was a tale of two halves for Taijuan Walker in 2021

Let’s hop into a time machine and travel back to February of this year, when free agent starting pitcher Taijuan Walker signed a two-year, $20 million contract with the Mets. If you told your past self the final numbers that would ultimately be on Walker’s stat line for the 2021 season—a 7-11 record with a 4.47 ERA over 159 inning in 30 games pitched—you’d probably say it sounded about right. Certainly not the best outcome we could have hoped for from a pitcher who has shown flashes of being better than that—say, in his career-best year with the Diamondbacks in 2017—but also not the worst case scenario for the first full season from a pitcher since coming back from Tommy John surgery.

In reality, however, the path that Walker took to get to that final stat line contained a much larger number of peaks and valleys than one might have expected. At times - predominantly in the first half - Walker looked as dominant as he’s looked in his entire big league career. At others - predominantly in the second half, and thus being our most recent and lasting memory of him - he looked like he didn’t belong in the major leagues. All told, it combines for a season which makes it difficult to project exactly what we can expect from Walker as he moves into the second and final year of his contract with the Mets in 2022.

After signing with the team, the Mets were really probably just hoping that their newest addition could serve as an adequate fourth starter in their rotation—behind the more established Jacob deGrom, Marcus Stroman, and Carlos Corrasco, but ahead of second-year pitcher David Peterson. In the early going, however, Walker looked like he was a much different pitcher. The shift was noticeable early on, as he seemed to have added some extra juice to his fastball velocity when compared to his recent seasons. In fact, that extra velocity was there throughout the entire season, even after his other numbers started taking a turn for the worse. His overall average fastball velocity was 94.5 MPH, his highest since 2016.

And it made a big difference in the early going, as Walker immediately proved to be an indispensable presence in the Mets’ rotation. While so many of the other players on the team went down to injury, he stayed largely healthy (save for one very brief IL trip in May, and he only missed the minimum amount of time for that). Not only did he provide stability, but he also provided a level of dominating production that, in all honestly, was probably not appreciated as much as it should have been at the time as a result of what his teammate deGrom was doing. Walker’s May was especially dominant—in five starts, he put up a 1.61 ERA with a 0.714 WHIP and a 5.20 SO/BB rate over 28 innings pitched, which played a pretty huge role in helping the Mets get out to their early division lead.

Walker was rewarded for his stunning first half with his first career All-Star nod after deGrom bowed out of the game. Naming him an All-Star might seem hard to believe now if one were to look at what his overall numbers on the season wound up being, but given what his overall numbers were at the end of the first half—a 2.66 ERA in over 94.1 innings in 17 appearances—it was an entirely deserved honor for Walker. He was both a stable and electric pitcher for the Mets, and that does deserve to be remembered despite how things would eventually play out.

Of course, anytime someone puts up those kinds of numbers which represent a significant difference in career norms over a short sample of games, one is bound to look at them with some level of skepticism. And his 3.94 xFIP in the first half might indeed have been an indication that some measure of regression was in order. However, it seemed reasonable at the time to think that Walker’s improvements might be legitimate. He was, after all, one of the very best pitching prospects in the game once upon a time, and he wouldn’t have been the first player to blossom at a slightly later stage in his career. Furthermore, the extra distance from his Tommy John surgery could also have been a boon for him and a potential explanation for the velocity increase, meaning there were reasons to hope that Walker’s production could remain far greater than what the Mets initially expected from him.

But immediately following the All-Star break, Walker—much like the rest of the Mets team—crashed down to Earth. The downslide started in his very first start out of the break, when he gave up 6 runs (5 earned) and did not make it out of the first inning against the lowly Pittsburgh Pirates. His next two starts, in which he gave up a combined 11 runs in nine innings, continued the dreadful trend. In just three quick starts, his ERA jumped from 2.66 to 3.81, and suddenly Walker didn’t look like much of an All Star at all.

He did at least slightly rebound from his dreadful 9.00 July ERA to have a more respectable August (4.15 ERA ERA in five starts over 30.1 innings). But then he had a September that was somehow almost as dreadful as his July (7.66 ERA in five starts over 24.2 innings). It’s hard to identify just one cause for his downfall in these later months, given that just about every element of his performance had worsened over the course of the season. Strikeouts went down (25 K% in the first half compared to 18.6% in the second half), walks (7.9% to 9.1%) and homers (0.57 HR/9 in the first half to 2.80 in the second) went up. Looking at the Baseball Savant stats over the course of the season led me to the very astute analysis that his pitches got clobbered a lot more later in the season (as just one of many potential examples: the barrel percentage on his four-seam fastball was at 13% in April, but was at a shocking 35.7 % in September). And of course, there is the pesky fact that Walker did not manage to secure a single win during the entire second half of the season.

Don’t get me wrong: pitcher wins are a bad and outdated stat. But an All-Star starting pitcher not even getting one in an entire half of baseball? That is not ideal and paints just about as bad a portrait of how Walker’s second half went as the more general stats (7.13 ERA over 64.1 IP in 13 starts) do.

The question is: Was this drop in production the result of fatigue from a pitcher who was still adjusting to a full season’s worth of innings after both his Tommy John recovery and the COVID-shortened season? Was it simply an expected regression for a pitcher who was putting up numbers that did not represent his career norms? Were there some injury issues that were causing him problems on the mound (the side tightness that sent Walker to the IL in May did result in him batting left-handed for a big portion of the remainder of the season; perhaps that issue also hampered him while pitching)? Regardless of the answer to that question, the result was devastating for the Mets. Walker quickly went from a reliable and sometimes dominant starter for the Amazins to one who literally could not win a single game. While those final season numbers seem at least passable at first glance, they become a huge disappointment when we consider how terrific Walker was for such a huge chunk of the season. And while the 2021 Mets fell apart for a large number of seasons, the consequence of throwing out a pitcher who continuously struggled the way he did cannot be overstated.

So where does Walker go from here? It’s hard to expect him to put up the kind of numbers we saw from him in that first half again, but the Mets do need to pray to the baseball gods that his abysmal second half was largely the result of fatigue and will not be repeated next year now that he’s built up his arm strength by pitching in a full season. As important as his role on the team was in 2021, it will likely be even more important next year with Marcus Stroman potentially departing in free agency and Jacob deGrom’s health still being a point of uncertainty after his injury-plagued season. The Mets need Walker to be a consistent, stable, and productive presence in the 2022 starting rotation. If nothing else, they certainly need him to show that his 2021 second half was an aberration, or else he may not survive the entire season and the Mets may be in-line for another disappointing year.