The space between potential and production for minor leaguers becomes most glaring at this time of the year, when their seasons are coming to an end. The chance to justify or defy expectations runs out, and every year there are players who land on each side.
“We’re never satisfied,’’ said Mike Hazen, the Red Sox’ director of player development. “There are certainly guys that played very well. There are guys that end the season not feeling like they had the year they wanted to have.’’
Our position-by-position choices for the best of the Red Sox farm system are based on which players had the best seasons, not which players will make the best pros. For example, first baseman Lars Anderson’s potential remains vast, but he and his .688 OPS at Double A Portland will not be making this team.
With that in mind, these were the best Sox minor leaguers this year:
First base - Anthony Rizzo, Greenville and Salem. Rizzo sat out most of last season after being diagnosed with limited-stage classical Hodgkin’s lymphoma. He returned to help lead Greenville to a first-half division title before his promotion to Salem, where he continued to hit. He batted .297 with 11 home runs and 48 walks during an inspiring season.
Second base - Kenneth Roque, Gulf Coast and Lowell. After starting his third year in the Gulf Coast League, Roque blossomed as a hitter. He put up a .400 on-base percentage and a .520 slugging percentage in 40 GCL games. During his first six games with Lowell, Roque continued his tear by batting .412. Roque made 10 errors, but he is improving; in 2007, he made five in one game.
Shortstop - Derrik Gibson, Lowell. One of the fastest players in the system, Gibson stole 27 bases while batting .294. He split time at shortstop and second base, but he earns this spot in part because of a thin field.
Third base - Jorge Jimenez, Portland. Jimenez was named to the Eastern League All-Star team, and though he tapered off a bit in the second half, he remained steady. His 13 home runs tied for second on the Sea Dogs, and he also hit 20 doubles and three triples.
Catcher - Luis Exposito, Salem and Portland. Catcher was a strong position in the Sox system this season, and Exposito narrowly edges out Tim Federowicz and Mark Wagner. All three impressed, but only Exposito’s performance improved after a promotion. In 21 games with Triple A Pawtucket, he hit .345 with three home runs. Exposito has the potential to be a power hitter. The Sox want him to improve his plate discipline.
Outfielder - Ryan Kalish, Salem and Portland. Kalish sputtered after an early promotion to Portland, but he quickly recovered. He totaled 15 home runs and stole 20 bases while playing excellent defense.
Outfielder - Daniel Nava, Salem and Portland. As a freshman in high school, Nava was 4 feet 8 inches and weighed 80 pounds. As a freshman in college, he washed uniforms and dragged the infield as a team manager. He went undrafted and caught on with the Red Sox after special assistant Allard Baird spotted him in an independent league. In his second year with the organization, Nava made clear the Sox discovered a gem. He missed the first part of this season with an injury, but in 56 games, his 1.004 OPS is the highest in the organization. In Portland, he is batting .371 with four home runs and 19 walks in 97 at-bats.
Outfielder - Josh Reddick, Portland and Pawtucket. The Red Sox added him to their roster Wednesday for the third time this year, and he earned his way to Boston. The ball launches off his bat when he sprays line drives from gap to gap.
Designated hitter - Ryan Lavarnway, Salem. While also playing catcher, Lavarnway hit 20 home runs, the most of any Red Sox minor leaguer, and batted .282. Lavarnway, who attended Yale, has the body to develop into a slugger at 6-4, 225.
Starting pitcher - Casey Kelly, Greenville and Salem. In half a season, Kelly went from a first-round pick in 2008 to perhaps the Sox’ best prospect in 2009. As a pitcher, he went 7-5 with a 2.08 ERA for Greenville and Salem while striking out 74 and walking 16. He also plays shortstop, but his poise and ability on the mound may decide his future.
Starting pitcher - Junichi Tazawa, Portland and Pawtucket. Tazawa gave the Red Sox everything they hoped for when they signed him out of Japan’s semi-professional Industrial League in the offseason. He became the ace of Portland’s staff and rapidly ascended to Boston, where he is in the starting rotation.
Starting pitcher - Alex Wilson, Lowell. The Sox chose Wilson in the second round this year, and he has validated that selection. In 13 starts, he has allowed two earned runs in 36 innings - a 0.50 ERA - while striking out 33. He was a reliever in college, but he will start for the Sox at least through the lower minor leagues.
Relief pitcher - Fernando Cabrera, Pawtucket. He spent time with Boston after being a bright spot during a dismal season for the PawSox. He saved 22 games while posting a 1.78 ERA and a 1.18 WHIP.
Relief pitcher - Derrick Loop, Salem and Portland: His pickoff move is so good that teammates joke he should walk batters intentionally and then pick them off. His pitching isn’t bad, either. He saved 16 games for Salem while compiling a 1.66 ERA. Promoted to Portland late in the year, he has allowed one hit and no runs in four innings.
Westmoreland, a Rhode Island native, hurt himself in only his eighth game playing the outfield. He played his first 52 with Lowell as a designated hitter, a precaution as he came back from another surgery, to repair a partially torn left labrum.
Westmoreland showed no ill effects. He batted .296 and hit a team-high seven home runs. In his brief time as an outfielder, he displayed his standout athleticism and impressed the Red Sox.
“You never really expect somebody to be that good when he came in,’’ Hazen said. “You never assume a young kid is going to be able to come in and do what he did. He exceed expectations.’’
Adam Kilgore can be reached at akilgore@globe.com 
