Not every rookie will leave his mark on baseball like Aaron Judge and Cody Bellinger did a year ago, but each club has a prospect or prospects who should crack its big league roster in 2018. Below are MLB Pipeline's choices for the rookies who will make the biggest impact on each team in the American League West.
• Impact prospects: NL East | NL Central | NL West | AL East | AL Central | AL West
Houston: J.D. Davis, 3B/1B (No. 9 on Astros' Top 30)
Opening Day 2018: Astros
Davis had to repeat Double-A at the start of 2017 because of Houston's wealth of third basemen, which was eased by the offseason inclusion of Colin Moran in the Gerrit Cole trade with the Pirates. He won't wrest the hot-corner job away from Alex Bregman, but an impressive Grapefruit League performance earned him a spot on the Opening Day roster and some playing time at first base while Yuli Gurriel is sidelined with a hand injury. Davis' strength creates power to all fields, as evidenced by 79 homers in three full pro seasons since signing as a third-round pick out of Cal State Fullerton in 2014, and he went deep four times in 62 at-bats with the Astros late last season.

Los Angeles: Shohei Ohtani, RHP/DH (No. 1 on Angels' Top 30; No. 1 on Top 100)
Opening Day 2018: Angels
Yes, he's struggled in acclimating to the game here this spring, especially at the plate. But the stuff on the mound is legit, so even if the bat doesn't get going, he's going to impact the Angels rotation. And beyond the numbers, if he can show the ability to play both ways at this level, he's going to change the game.

Oakland: A.J. Puk, LHP (No. 1 on A's Top 30; No. 32 on Top 100)
Opening Day 2018: Triple-A DL
Puk looked like a dark-horse candidate to crack Oakland's Opening Day rotation up until he recently was shut down with biceps tendinitis. The big left-hander showed why he's such a big piece of the A's future before that, allowing one or fewer earned runs in three of his four Cactus League outings. After averaging 13.2 strikeouts per nine innings and reaching Double-A in his first full season, Puk, once healthy, could ascend to the front of Oakland's rotation in 2018.

Seattle: Daniel Vogelbach, 1B (No. 11 on Mariners' Top 30)
Opening Day 2018: Mariners
Vogelbach has struggled to find consistency over parts of two seasons in the big leagues with Seattle, hitting just .175 in 40 at-bats and 24 games. But a monstrous spring has the big first baseman's stock pointing up ahead of the 2018 season, so much so that he already has been named to the Mariners' Opening Day roster. He'll compete for at-bats once Ryon Healy returns from injury, but Vogelbach's power and on-base skills from the left side could make him a valuable, yearlong contributor.
Texas: Willie Calhoun, OF (No. 2 on Rangers' Top 30; No. 53 on Top 100)
Opening Day 2018: Triple-A Round Rock
The best of the three prospects Texas acquired from the Dodgers in exchange for Yu Darvish last July, Calhoun combines hitting ability and power better than most prospects. The Rangers have made the former second baseman a full-time outfielder and he should emerge as at least a platoon player in left field early this season. He makes consistent hard contact from the left side of the plate and lets his pop come naturally, a mature approach that resulted in more extra-base hits (64, including 31 homers) than strikeouts (61) in Triple-A last year.