Most surprising, disappointing MLB players in 2018

While he's currently on the DL, Cervelli has the second best WAR among all catchers after hitting .257/.390/.486 with great defense. While he has one year remaining on his contract, the Pirates could look to sell high this month if Cervelli gets healthy.

Coming off one of the best offensive seasons of his career, Avila cashed in with Arizona on a two-year, $8.25 million contract. He's hit a pitiful .124-3-7 with 54 strikeouts in 121 plate appearances during the first half and is now on the DL with a hamstring injury. The Diamondbacks have made John Ryan Murphy their starter and surely regret buying high on Avila.

Aguilar had a breakout 2017 season as a platoon player against lefties, but he's been much more than that this year. Picking up playing time when Eric Thames was injured, Aguilar is now among the NL leaders in slugging percentage (.617) and is hitting .308-19-55 in only 259 plate appearances. He's convinced the Brewers to keep him in the lineup.

While Davis has shown signs of decline recently, no one saw this coming. He's been historically awful in the first half, hitting just .153-7-24 with a .489 OPS. That's good for a -2.2 WAR, and he's on pace for one of the worst offensive seasons in history. Oh, he also has four years and $92 million left on his contract after this season.

Lowrie has long been a quality role player but injured all too often. He's been on a rampage since the start of this season, however. Lowrie has been one of the best second basemen in the game, hitting .293-14-59 with an .857 OPS over his first 84 games, holding off hot prospect Franklin Barreto in the process.

With Dustin Pedroia's health unclear, the Red Sox brought back Nunez on a one-year, $6 million contract this year. Even though Pedroia has played just three games, the contract looks like a mistake. Nunez is showing a steep decline at age 31, hitting .254-6-22 with only four stolen bases in 72 games. His .657 OPS is the worst of his career.

Suarez is developing into a star and has been one of the few bright spots on a bad Cincinnati team. He leads the NL in RBI despite missing over two weeks in April to a wrist injury, hitting .305-17-63 with a .964 OPS.

Donaldson has been a star since 2013 and had his sights set on a big season in his walk year. Unfortunately, he's been limited to only 36 games due to injuries and has hit only .234-5-16 when he has been able to play. The struggles will certainly hurt his market this offseason.

Escobar proved to be a quality offensive player last season with 21 home runs, and the Twins were counting on him in the first half of this season with regular shortstop Jorge Polanco suspended for 80 games for PEDs. Escobar has been everything the Twins could have hoped for, hitting .274-12-49 and leading the AL with 34 doubles. His .855 OPS is nearly 100 points higher than last season.

Arcia looked like a budding star in his first full season in 2017, but he's regressed considerably this year. The speedy shortstop has hit just .197/.231/.251 in 212 plate appearances and has put the team in a bind to find a viable replacement while Arcia finds himself at Triple-A.

Kemp was on the decline when he was traded from the Braves to the Dodgers in an offseason salary dump. In fact, there was no guarantee that Kemp would even make the roster after posting a .781 OPS with poor defense last season. He showed up to spring training in much better shape this year, and it's shown both at the plate and in the field. He's effectively been the team's MVP, hitting .318-15-55 with a .911 OPS and been more than adequate in left field.

Gonzalez played himself into a regular role for the World Series champs last season, hitting .303-23-90. Based on his track record, there was reason to be skeptical, and Gonzalez has proven the skeptics correct by hitting only .230-6-34 through 78 games. His versatility still has been valuable, appearing at all four infield positions this year in addition to the outfield.

Martin has been a relative disappointment since coming over from Cuba, failing to post a .700 OPS in the majors before this season. He signed with the Tigers for only $1.75 million for the promise of regular playing time and has made the most of it, hitting .257-9-29 with seven steals and a .758 OPS while playing quality defense.

Few players performed better than Buxton during the second half of last season, when he hit .300-11-35 with 13 steals and played Gold Glove defense. Unfortunately, injuries have plagued him early this season, and he's hit just .156 with no home runs in 94 plate appearances when he has been on the field.

A quality, "professional" hitter before this season, Markakis had become a liability for the Braves offensively due to his lack of power. He had just a .743 OPS in his first three seasons with Atlanta, but Markakis has been on fire at age 34 this season. He has an .890 OPS and leads the NL in hits (108) and doubles (27) while also posting more walks than strikeouts.

With apologies to Dexter Fowler, Calhoun has been the worst and most disappointing right fielder in baseball this season. Through 64 games, the usually sturdy outfielder is hitting just .171-4-16 with a .476 OPS. It's unclear what's wrong, but the poor play has caused Chris Young to see more playing time as a result.

After three successful seasons in Japan, Mikolas announced his intent to come back to the U.S. this season. The control pitcher struggled in his first MLB stint before going to Japan, so he managed just a two-year, $15.5 million contract with the Cardinals. Mikolas' pinpoint control has allowed him to become the ace of the St. Louis staff, going 8-3 with a 2.61 ERA and 0.99 WHIP through his first 16 starts of the year.

Most Royals fans knew the team would be bad this season, but at least they had some building blocks like Duffy to count on. That's what they thought, anyway. The lefty has been terrible this season with a 5.19 ERA and 48 walks in his first 100.2 innings spanning 18 starts.

Colorado was active in free agency this offseason by signing relievers Wade Davis and Bryan Shaw, but Ottavino has been the best contributor. After struggling with his control and posting a 5.06 ERA last season, Ottavino has been electrifying in the first half with a 1.88 ERA, 0.91 WHIP and 14.1 K/9. The results are even more impressive considering he's appeared in 14 games at Coors Field.

Shaw left Cleveland for big money this offseason, signing a three-year, $27 million contract to become the Rockies' setup man. Unfortunately, Shaw has been nothing short of a disaster with the move to Colorado. He has a 7.57 ERA and 1.96 WHIP in 35.2 innings, allowing 50 hits. After making 70-plus appearances in five straight seasons and leading the AL in three of those seasons, it looks like the workload has caught up to Shaw.

The Cardinals signed Greg Holland to be their closer on Opening Day, but he hasn't pitched well enough to gain the role. Fortunately, Norris has come up big as an MLB closer for the second straight year. The right-hander has 16 saves and a 3.03 ERA, and his peripherals show an even better pitcher with 46/5 K/BB in 35.2 innings.

Neris opened the season as Philadelphia's closer, but that didn't last long. While he's converted 10 saves, Neris was removed from the role in mid-May and has a 6.90 ERA with 11 home runs allowed in 30 innings. As a result, he's already been demoted to the minors twice this season.

The Braves came into the year loaded with young talent, but they weren't expected to be ready to challenge the Nationals yet. Instead, they lead the NL East through 84 games with the second-best run differential in the NL. Snitker has helped develop the team's youngsters, getting breakout performances from Ozzie Albies, Ronald Acuna Jr., Mike Foltynewicz and Sean Newcomb.

The Orioles looked bad on paper coming into the season, especially their rotation, but few could have expected them to play this poorly. Through 84 games, Baltimore is 32.5 games out in the AL East with an awful -124 run differential. Certainly, Showalter can't shoulder all the blame for the team's regression, but fans expected better with stars like Manny Machado and Adam Jones in the lineup.