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Is Yonder Alonso back on track?

After finally having surgery for a lingering forearm issue, Padres' first baseman Yonder Alonso is off to a resurgent 2015. How did the injury affect his past performance, and is this hot start sustainable?

The Padres' Yonder Alonso is healthy after battling an injury for a season and a half.
The Padres' Yonder Alonso is healthy after battling an injury for a season and a half.
Jake Roth-USA TODAY Sports

San Diego Padres’ first baseman Yonder Alonso was one of the club's overlooked pieces when A.J. Preller transformed the team in the off-season. A former top prospect of the Reds, Alonso arrived in San Diego as a piece of the blockbuster Mat Latos trade. His profile was that of a first base-only defender with outstanding plate discipline and some modest power projection, not dissimilar from Joey Votto, the man blocking him out of Cincinnati.

Despite moving to Petco Park, Alonso produced at an above average rate in his first year and a half in San Diego. Despite hitting only 9 HR in 2012, his 39 doubles and 10.0% BB / 16.3% K rates helped lead him to an above average 110 OPS+ in his first full season. The two years that followed were more of a struggle. Hit on the hand by a pitch on May 31, 2013, Alonso missed significant time in both that season and 2014 with hand and forearm injuries. During this time, his on-field production was a noticeable decline from his prior work.

Pre-Injury 958 .279 .346 .410 .756 .321
Injury Period 451 .253 .308 .365 .673 .272

In the first month of 2015, Yonder Alonso’s stat line is features more walks (11.1 percent) and a high average (.333), while keeping strikeouts down (13.3 percent) as of May 1. He’s started in 21 of the Padres’ 24 games, and his 148 OPS+ is among team leaders. This apparent resurgence leads to a few questions: Does Alonso’s injury potentially explain his struggles? Is he finally healthy? Is this torrid start sustainable?

With regard to the first question, I believe a convincing hypothesis can be constructed. Here is an expanded view of the above split, including some batted ball data and pitches seen.

Pre-Injury .756 59.8% .321 16.9% 9.1% 45.8% 28.1% 21.5% 4.6%
Injury Period .673 61.6% .272 11.8% 7.5% 44.1% 23.1% 26.7% 6.1%

Something noticeable here is Alonso’s further improved strikeout rate during his injury. In 2014, he displayed then career-best contract rates (94.5 percent Z-Contact %, 64.5 percent O-Contact %) despite the lingering forearm injury that would end his season.

It appears that extra contact may have also been weaker contact. He experienced below career-average BABIPs on every batted ball type, culminating in a low .272 rate during those 18 months. Additionally, his fly ball percentage dropped, and a higher percentage of those fly balls were pop ups. Pitchers appeared to respond to this weakened contact by throwing Alonso more strikes, at a rate (1.8 percent more) fairly in line with his drop in walks (1.5 percent fewer).

It appears that as many would predict, an injured forearm would result in weaker contact from the afflicted batter. Pitchers responded to this injury, and while his plate discipline actually improved, Yonder Alonso walked less often and made more outs despite his contact rate.

It may seem a stretch to connect two different DL stints, with two different injuries, over two different seasons. Alonso first missed time in 2013 with a fractured hand, and followed that with a torn tendon in his forearm in August 2014. How can one be confident to connect the two incidents?

Via U-T San Diego, Yonder Alonso himself attributed both to the same event:

"People talk about injuries. They say, ‘You’re injury-prone,’" Alonso said. "At the end of the day, it was one injury. I was hit by a pitch. With that being said, it took a little long (to recover).

In terms of his present-day health, Alonso is completely is completely confident in his recovery. In the same comments linked above, he reveals that he only had surgery to fix his forearm issue this past off-season. Any on-field performance (127 games) between the initial hit-by-pitch and the surgery was likely affected by the injury.

This brings us to the final of the questions posed earlier: Is Yonder Alonso’s hot start in 2015 sustainable? As much as it sounds like a cop-out, his success likely won’t continue in the same manner, but there’s a chance it regresses to a more traditional definition of success.

90 60.2% .333 .411 .436 .847 .379 13.3% 11.1% 65.7% 16.4% 17.9%

Through May 1, Yonder Alonso is sporting a high .379 BABIP, which alone doesn’t say much. However, with a batted ball profile consisting of 65.67 percent ground balls, that figure seems due for regression. It seems particularly flaky when his current .302 ground ball BABIP is considered (and for a batter who has been worth -1.2 BsR in a month, that seems unsustainable). His power has also yet to appear, with only a .102 ISO and 5/24 hits going for extra-bases.

Despite his current success appearing unsustainable, there are positive signs toward the remainder of the season. Alonso’s plate discipline has remained, and as pitchers have returned to near his pre-injury strike rate, he has found ways to take even more walks. Additionally, his batted ball profile is due for regression. His 65.67 percent ground ball and 16.42 percent fly ball rates are far from both league and career averages. While his performance on ground balls is unsustainable, it is possible that he relies on them less as the season wears on. With more fly balls and line drives added to his production, Alonso should demonstrate power commensurate with his pre-injury profile.

He may never be a superstar, but finally healthy, Yonder Alonso can still be an above-average bat in a very difficult ballpark. At the end of the season, it’s possible that the addition of a healthy first baseman could be the Padres’ most underrated acquisition of the off-season.

. . .

All statistics courtesy of Baseball ReferenceFangraphsBaseball Savant, and The Baseball Cube.

Spencer Bingol is a Contributor at Beyond the Box Score. You can follow him on Twitter at @SpencerBingol.