In 1995, a young Portland Sea Dogs outfielder named Billy McMillon put together a .423 on-base percentage, and he didn’t even notice it.

“It wasn’t something I was working toward,” said McMillon, now the Sea Dogs manager.

“I was aggressive to my pitch, walking more than I struck out. It’s something Mookie is doing now – except he’s hitting 100 points higher.”

Mookie Betts, 21, is Portland’s second baseman. Betts not only is batting .383 with a .452 on-base percentage, he put together an on-base streak of 66 regular-season games.

That streak ended Saturday when Betts went 0 for 4 in a 4-3 win over Trenton.

“The streak is over. That’s all right. (Time to) start a new one,” said Betts, who did have two RBI on groundouts.

“Trying to impact the game some way.”

Betts came five games short of the minor league streak record of 71 games, coincidently held by two former Sea Dogs, Kevin Millar and Kevin Youkilis. Both streaks involved games in Portland and in Triple-A.

Betts’ streak began last year in Class A Salem. Counting five playoff games, Betts’ streak was 71, but baseball records don’t include the postseason.

The minor league on-base streak record may be official, but it is not conclusive. Minor League Baseball officials could not provide a list of streaks before Millar’s, which began in 1997.

Steve Densa of Minor League Baseball (MiLB) emailed that “in most cases, we cannot definitively say whether an accomplishment is the longest, most, etc., in MiLB history because our records do not go all the way back to our first season in 1902.”

Other record books do not offer much on on-base streaks. That is because the idea of getting on base, as opposed to getting a hit, was not popularized until recently.

“It’s an evolving principle,” McMillon said.

On-base percentage became common language, especially with the best-selling book (and movie) “Moneyball.” In the book, Oakland A’s General Manager Billy Beane referred to Youkilis as the “Greek god of walks.”

The Betts evolution

Youkilis never liked that reference because he maintained he was not trying to walk. Betts feels the same way.

“I’m not up there looking for a walk. I want to hit something hard,” Betts said. “I’ll take a walk to get on base. That’s what a leadoff hitter is supposed to do.”

If Betts keeps up with his on-base percentage, he will have the second-best mark in Sea Dogs history, behind Youkilis’ .487 (2003). McMillon (’95) and Millar (’97) have the next best, both with .423.

When Betts was drafted out of Overton High School in Nashville, Tennessee, in 2011 (fifth round) he was not a free swinger.

“I took a lot of pitches. Kind of where I got in trouble because these (professional) pitchers will eat you alive if you give them strikes,” Betts said. “I’m trying to get a little more aggressive, but aggressive to my pitch.”

Betts batted only .267 at rookie-league Lowell in 2012, and began 2013 hitting .150 over the first 24 games at low Class A Greenville.

Time for a change. Betts’ batting stance featured a high leg kick (“like a pitcher,” Betts said) with his lead (left) leg.

Using a leg kick may appear to help with timing, “but it can be less consistent,” said Betts’ teammate, Travis Shaw, who ditched a high leg kick last season and is batting .301 this year.

In Greenville last year, hitting coach U.L. Washington told Betts to lower the kick to more of a step.

“I just trusted that it might work,” Betts said. “It couldn’t get any worse.”

It got better, much better. With better timing and balance, Betts hit .355 for the next 51 games before being promoted to advanced Class A Salem. There he hit .341 with a .414 on-base percentage.

But that was in Class A. Double-A pitchers feature more polish. How would Betts fare? The answer is in his numbers, including the on-base streak.

“That’s not just hitting. It’s the whole package,” Sea Dogs hitting coach Rich Gedman said. “You’re looking at discipline. You have to catch some breaks sometimes. It’s usually someone with a good eye who will take a walk. They don’t look for it. They earn it.

“You have to pitch to them. If you don’t throw it over the plate, they’re not going to swing.”

Shaw, who is second on the team in on-base percentage (.398), observes Betts with admiration.

“He’s never fooled. He’s never off balance. He can handle any pitch in the zone,” Shaw said. “He can pull it with power, or he can flip it to right. His eye is remarkable, too. He doesn’t chase out of the zone.”

Where to from here?

Betts will eventually change locations, in terms of team and position.

If he keeps up this performance, it will force a promotion. Betts played his 37th game for Portland on Saturday. Jackie Bradley Jr. (61 games), Garin Cecchini (66) and Dustin Pedroia (66) are among those who briefly spent time in Double-A.

Ben Crockett, Red Sox director of player development, was in Portland Friday to watch the Sea Dogs. Betts has obviously impressed the boss.

“Day in and day out, the quality of at-bats; the consistency from one day to the next; and the ability to make adjustments from one at-bat to the next, has been really impressive,” Crockett said.

“Obviously a somewhat short sample size, but nonetheless it’s getting bigger.”

So, speaking of Pedroia, does Betts eventually move away from second base? During Portland’s batting practice, Betts has fielded balls at shortstop and center field.

“Any time we’re at the upper levels, (changing positions) is always on the table; something we’re discussing, not just with him but with any player,” Crockett said.

“We have a unique situation, given our second baseman in the big leagues … Given (Betts’) athleticism and his approach to the game, his level-headed approach and embracing of any challenge, when and if that time comes (to change positions), he’ll handle it appropriately.”

The Red Sox will find a spot for Betts. There’s always a place for a player who knows how to get on base.

Kevin Thomas can be reached at 791-6411 or at:

kthomas@pressherald.com

Twitter: ClearTheBases