Jeremy Rivera, right, has played at second, third and short for the Portland Sea Dogs, making only six errors in 77 games this season. “He’s a major league fielder,” says Sea Dogs Manager Joe Oliver. Brianna Soukup/Staff Photographer

A season that started out promising is coming to an end this weekend for Portland Sea Dogs infielder Jeremy Rivera. The team’s final four-game series begins Friday night against New Hampshire at Hadlock Field.

Rivera, 24, has always been known for his glove – “He’s a major league fielder,” said Sea Dogs Manager Joe Oliver – but his bat has been average-to-below average in the minors. Last year, he batted a career-best .262 in his first year at Double-A.

In his first five games this year, Rivera seemed poised for a breakout season, going 6 for 15 with a double and home run. It was an impressive start for an infielder battling for playing time on a team that featured three other infield prospects – third baseman Bobby Dalbec, shortstop C.J. Chatham and second baseman Brett Netzer.

On April 16 in Reading, Pennsylvania, he remained on fire. Rivera singled in the first inning, homered in the third and added another RBI in the fifth with a sacrifice fly.

But in the bottom of the seventh, Reading’s Luke Williams scorched a grounder to third base. Rivera thought he had it lined up.

“Bad hop,” he said.

The ball bounced hard into Rivera’s face, breaking his nose.

“First time, I’ve been hurt in my career,” said Rivera, a 17th-round draft pick by the Boston Red Sox in 2014. He remained on the injured list for three weeks. Rivera said he later hurt his shoulder while diving for a ball but was able to stay activated.

But whether the injuries bothered him or he’s just slumping, Rivera was batting just .228 heading into Thursday night’s game at Binghamton.

In the field, Rivera has made only six errors in 77 games. He’s spent most of his time at his natural position, shortstop, but he’s also played 13 games at second and 22 at third base – the first time he’s played that position.

“He can play anywhere,” Oliver said. “He has great instincts.”

Rivera also shows off a strong arm. But he knows where he has to improve.

“Hitting,” he said. “Have to keep it simple. Last year was very good. I was putting the ball in play.”

Utility players who play strong defense are coveted at the major league level – but they need to hit.

When Tzu-Wei Lin came to Portland at the end of the 2015 season, he was considered a prospect, but he hit only .202, and then .223 in 2016. Lin batted .302 in 2017 and reached the majors that year.

Rivera is Rule 5 eligible after the season, but a longshot to be drafted. He will not be a minor league free agent for two more seasons, and is likely to return to Portland next year.

THE ARIZONA FALL League, the annual showcase of prospects, begins Sept. 18. Of the six Red Sox prospects named to the league, five are former or current Sea Dogs – Pawtucket pitcher Tanner Houck and shortstop C.J. Chatham, and Portland pitcher Bryan Mata and outfielders Jarren Duran and Marcus Wilson. The sixth, left-hander Yoan Aybar, was just promoted to advanced Class A Salem. Aybar, 22, was an outfielder for four seasons before moving to the mound last year. He struck out 67 and walked 40 in 51 2/3 innings in lower Class A Greenville.

Chatham, Wilson and Aybar are all eligible for the Rule 5 draft this December, unless added to the 40-man roster.

Dalbec, now with Triple-A Pawtucket, played in the AFL last year.

TRISTON CASAS is likely to land in the AFL in coming years. In his first full pro season, the 2018 first-round draft pick continues to impress. Casas, 19, is hitting .324 in his last 10 games with Greenville. He is likely bound for the Florida Instructional League in the offseason and will probably begin next year in Salem. Depending on his results and how much Boston wants to push him, he could see Portland by the end of next season.

RED SOX FANS will want to check out the book “Homegrown” by Alex Speier, a sports writer who has covered the Red Sox and their minor league system for several media outlets, most recently The Boston Globe. Speier appeared at Hadlock Field recently, throwing out the first pitch and signing copies of his book. The book is full of information and behind-the-scene tales. The chapter on Mookie Betts is enlightening, including Betts giving thought to playing college basketball because he was slumping so bad at the start of the 2013 season while still in Class A.