Major League clubs are constantly looking for ways to upgrade the roster via outside additions. But internal improvements can also play a big part in a team making a significant year-to-year leap.

Just look at the Twins in 2019. Sure, they brought in Nelson Cruz and several other solid veterans. But the biggest reason Minnesota went from 78-84 in 2018 to 101-61 last season is that Jorge Polanco, Max Kepler, Mitch Garver, Miguel Sanó, Byron Buxton, Jake Odorizzi and José Berríos increased their collective FanGraphs Wins Above Replacement total by 16.7 from the previous year.

The nine hitters below didn't live up to expectations in 2019, whether it was due to injuries, a regression in skills, bad luck or a combination of the three. Their teams are depending on a reversal of fortune in 2020.

José Ramírez, 3B, Indians

After consecutive third-place finishes in the American League MVP Award voting, Ramírez took a step back in 2019, hitting .255/.327/.479 (106 OPS+) with 23 home runs in 129 games. But the infielder's final numbers were depressed by a slow start. Ramírez looked like his old self for more than two months before a fractured right hamate bone landed him on the injured list, posting a .313/.360/.643 slash line with 41 extra-base hits (16 homers) in 60 games from June 14 through Aug. 24. Although the Tribe traded Corey Kluber and may deal Francisco Lindor as well, the 27-year-old Ramírez could help the club stay in contention if he can provide that type of elite production throughout 2020.

Manny Machado, 3B, Padres

The first season of Machado's 10-year, $300 million contract with the Padres was a bit of a disappointment. While he hit 32 home runs and provided a capable glove at the hot corner, his wRC+ dropped to 108 (140 in 2018), and he was worth 3.1 fWAR (6.2 in '18). San Diego went 70-92, finishing in last place in the National League West for the third time in four years. That said, Machado's hard-hit rate (78th percentile) and average exit velocity (87th percentile) were still strong, and he remains firmly in his prime at age 27. Machado has a good chance to recapture his All-Star form in 2020, and San Diego needs him to do so if it is going to make a playoff run.

Giancarlo Stanton, OF, Yankees

The Yankees showed the ability to overcome a spate of injuries in 2019, winning 103 games despite putting a big league-record 30 players on the IL. Stanton played just 18 games, as he dealt with a left biceps strain, a left shoulder issue, a left calf strain and a right knee sprain during the regular season before battling a right quad strain in the playoffs. Although New York has enough talent to get by if Stanton misses time again, the club's World Series title hopes may partly depend on the 30-year-old's health. Another lost season for the veteran slugger would also be incredibly troubling for the organization as a whole, considering Stanton is still guaranteed $244 million through 2027.

Joey Votto, 1B, Reds

After posting MLB's highest ERA (4.77) from 2015-18, the Reds flipped the script in '19, tying for the game's eighth-best mark (4.18). However, Cincinnati's offense was among MLB's worst, and Votto's decline was one of the driving forces behind the team's struggles. The first baseman recorded the lowest wRC+ (101) of his career, as his strikeout rate spiked (career-high 20.2 percent) and his walk rate plummeted (12.5 percent). Votto has hit just 27 home runs combined in more than 1,200 plate appearances over the past two seasons, and a return to his previous heights in the power department might not be coming at age 36. But Votto thinks the adjustments he made late last season put him in position for a rebound campaign in 2020. The Reds are counting on it.

Justin Upton, OF, Angels

The Angels have added Anthony Rendon, Dylan Bundy and Julio Teheran this offseason, but the club's offense remains extremely top-heavy, and its rotation is still a question mark. Upton can help alleviate the first issue by rebounding from a 2019 season in which he hit just .215/.309/.416 with 12 homers in 63 games. The 32-year-old was physically compromised, as he battled right knee soreness and a turf-toe injury in his left foot throughout the year. Upton was an above-average hitter (123 wRC+) with some excellent underlying metrics as recently as 2018, so it's not far-fetched to think he can return to form with better health.

Khris Davis, DH, A's

After producing a 129 wRC+ with a big league-leading 133 home runs from 2016-18, Davis finished with only 23 round-trippers and an 81 wRC+ in '19. But a closer look reveals that the veteran slugger was on pace for a fourth straight 40-homer campaign before suffering a left hip/oblique contusion in early May. The issue lingered, and Davis was placed on the IL several weeks later. Although he returned quickly, he hit .207 with 11 homers and a .616 OPS over 90 games the rest of the way, suggesting he wasn't fully healthy. Steamer sees a rebound effort on the horizon, projecting the 32-year-old for 39 homers and a 114 wRC+ in 2020. As the highest-paid player on a team with one of the lowest payrolls in MLB, Davis could be crucial to Oakland's chances of earning another playoff berth in a division that will likely be more competitive next season.

Lorenzo Cain, OF, Brewers

Cain remained a standout in center field last season, winning his first Gold Glove Award after recording 20 Defensive Runs Saved and 14 Outs Above Average. However, he dropped from a .301/.361/.433 slash line over 2014-18 to a .260/.325/.372 showing in '19. A right thumb injury might have been the root cause of his struggles early on, but he didn't exactly excel after undergoing a cryotherapy procedure in June. Given the departures of Yasmani Grandal, Mike Moustakas and Eric Thames, the Brewers are depending on Cain to provide more offensive production in 2020. Last year's .290 expected batting average and .330 xwOBA (.289 xBA, .342 xwOBA in 2018) suggest the 33-year-old has the skills to bounce back.

Matt Carpenter, 3B, Cardinals

Carpenter recorded career-best marks in homers (36), slugging percentage (.523) and OPS+ (143) in 2018, and his Statcast metrics backed up the production. The veteran also had a strong track record in the years before that, posting a 131 OPS+ from 2012-17. That made his 2019 decline all the more curious. Carpenter hit .226/.334/.392 (91 OPS+) with 15 home runs in 492 plate appearances, as his barrel rate, hard-hit rate, xSLG and xwOBA all plummeted. The Cardinals lost Marcell Ozuna to free agency and haven't made any notable offensive additions this offseason, which means the club is relying on a rebound effort from the 34-year-old Carpenter.

Andrew Benintendi, OF, Red Sox

Benintendi looked like a perennial All-Star in the making in 2018, hitting .290/.366/.465 (123 OPS+) and racking up 15 DRS in left field for a Red Sox club that ended up winning the World Series. But like many others in Boston last season, Benintendi regressed. With his chase, whiff and strikeout rates all increasing by a considerable margin, the youngster posted a .266/.343/.431 batting line (100 OPS+) over 615 plate appearances. The Red Sox have been largely dormant this offseason as they explore ways to trim the payroll, placing increased importance on players such as Benintendi turning things around in 2020. He's still just 25, so there's hope he can have a similar rebound to the one Rafael Devers experienced in 2019.