Like several others in Boston’s system, Sea Dogs infielder Mike Miller has produced at every level despite his size.

Going into his freshman baseball season in high school, Mike Miller was 4-foot-10, 95 pounds.

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Mike Miller connects for a home run Sunday – part of a 3-for-4, four-RBI day. Miller is hitting .303 with three homers and 12 RBI in 22 games since his promotion to the Sea Dogs.

“I was always the smallest guy on the team,” Miller said.

It’s a wonder the Boston Red Sox did not start scouting him then. Miller, now 5-9, 170, seems to fit the profile of players the Red Sox like – from 5-8 Dustin Pedroia and Sean Coyle, to 5-9 Mookie Betts, to 5-10 (barely) Brock Holt.

Smallish players with something to prove.

Miller, 24, is one of the latest additions to the Portland Sea Dogs and will be counted on to help the team’s drive for the Eastern League championship.

Miller is doing his part so far, batting .303 in 22 games, including a stellar effort Sunday afternoon.

Miller was a triple short of the cycle, with a home run, a three-run double and a single in the Sea Dogs’ 6-2 win over the Harrisburg Senators.

Miller also played second base flawlessly – the way he normally also plays short or third base when called upon.

“Look at Mike Miller anywhere on the field and he’s where he’s supposed to be,” Sea Dogs hitting coach Rich Gedman said. “There’s a keenness about him. His baseball knowledge is well above average.”

Ask Gedman about Miller’s hitting approach, and Gedman does not go into technical-speak about stances and swing paths.

What makes Miller successful?

“Determination,” Gedman said. “He’s always been the little guy. He makes up for it. … There’s a stick-to-it-ness, the will to succeed.

“He’s not going to (fail) from a lack of working.”

But there was a question if Miller was going to get the chance. Miller hails from Concord, California, about 20 miles northeast of Oakland. He had few offers to play baseball in college after he graduated from high school.

“I wasn’t highly recruited,” he said. “I had some injuries (in high school). Plus, I was the little guy.”

Miller opted to attend California Polytechnic State in San Luis Obispo as a student only. He liked the academics of the school, but there was a void.

“I was missing baseball,” he said.

Miller played baseball for a junior college team the next year and then returned to Cal Poly as a student and athlete. He batted .354 his senior year with an .898 OPS.

Every year, Cal Poly played a series against Fresno State, which had pitcher Justin Haley, now a Sea Dogs teammate.

“We didn’t scout much, but we knew (of Miller). They told me ‘their shortstop is unbelievable and (he’s tough to) get out.’

“He was the hardest out in the lineup. He doesn’t get fooled often. You really have to mix your stuff.”

Haley became a teammate of Miller’s in the Alaskan summer league and then, in the 2012 major league draft, both were chosen by the Red Sox, Haley in the sixth round and Miller in the ninth.

Miller began 2013 in low Class A Greenville and was hitting .356 in 15 games when he tore a quadriceps muscle and missed the rest of the year.

In spring training this year, Miller broke the hamate bone in his hand and missed the first two months. Then, after two months at advanced Class A Salem (.307 average), he was promoted to Portland in August.

On Sunday, Miller swatted a slider over the left-field wall for a home run in the first inning. He then broke a 1-1 tie with two outs in the fifth, lining a change-up into left-center for his bases-clearing double.

Another new guy contributing to the Sea Dogs, Miller has fit in well.

“It’s a pretty relaxed bunch of guys. Easy to get acclimated,” Miller said.

“And we’re playing loose right now. It’s all clicking.”