When Commissioner Rob Manfred said last month he’s looking at limiting pitching changes to quicken the pace of games, managers and others in the industry rolled their eyes.

But in the same interview Manfred brought up another idea that got far less attention but that is far more realistic.

Manfred said he’s a “big fan” of a 20-second pitch clock, adding it “would be one of those things that would keep pace of play in the mind of pitchers without really changing the behavior in a huge way.”

This would be a rule that both batters and pitchers would need to follow. Batters couldn’t go all Nomar Garciaparra — forever tugging, adjusting, mortifying — and pitchers couldn’t spend a half day getting in the right mental frame to throw the ball.

The rule, which basically calls for 20 seconds between pitches, is being auditioned in the minor leagues. A ball is assessed if the pitcher loafs, a strike if the batter is too slow to get in the box.

“Yeah, I think there’s a chance,” said Ed Montague, an umpire supervisor, when asked if the 20-second rule is coming to the majors. “I’ve seen it in the minors, and it’s working.”

The replay system is a huge drag on the game pace and needs to be tightened, including the time a manager is given to challenge a call and the actual time it takes to review a call.

Time between pitches is another matter. There’s already a between-innings clock, which has become hardly noticeable. One team jogs off the field, the other jogs on. The pitcher takes his warm-ups. Game on.

The pitch clock is trickier. Baseball can remain a leisurely sport with a quicker pace. Take the games in Oakland the past week, for example: Three straight games, beginning Monday, were under 2½ hours, and Friday’s was 2:19.

The only game surpassing three hours was Thursday’s, and the pace was fine. Here’s proof: I sat in the crowd with two 14-year-olds, and both refused to leave their seats.

Such a streak of quickness is rare. The average time of games through Friday was 3:00.04 — four minutes slower than last year’s and nearly a half hour slower than 1981’s.

But this isn’t about time of game as much as pace of game — avoiding long, unnecessary lulls.

The independent San Rafael Pacifics experimented with a clock in two games last weekend, and everything was timed. In fact, the game itself had a 2½-hour limit, apparently the first professional game in history with such a restriction.

Mike Shapiro, a former Giants legal counsel who runs the Pacifics, called it a “terrible idea, the worst idea in baseball ever. But with everyone talking about pace of game, we decided let’s give it a try, see how it works.”

In one game, the Pacifics were down a run through eight innings with one minute and 28 seconds left on the clock. If the ninth inning didn’t start before the clock expired, the Pacifics wouldn’t get their last ups. So they hustled onto the field (the catcher had been on base and quickly threw on his gear) in time to start the ninth.

The other game was tied when the clock expired and required an international tiebreaker to determine the outcome.

Shapiro is right. It is a rotten idea. But from the experiment came validation of the 20-second clock, in Shapiro’s mind.

“Of all the things we did, that was the most effective tool for pace of play,” he said. “It really speeds it up. Several times, pitchers and hitters were assessed with penalties. I don’t recall anyone beefing about it. I would suggest MLB take a look at it.”

Montague said that the threat of pitchers and hitters getting assessed a ball or strike for lingering would force them to adjust and be more prompt.

The 20-second rule being tried out in the high-level minors has reduced times of games. The pitcher must begin his windup or begin to get in the set position within 20 seconds of receiving the ball. The batter must be in the box and “alert to the pitch” with five or more seconds left on the clock.

The clock resets if a pitcher attempts a pickoff or steps off the rubber, or if time is called.

There’s already an MLB rule (Rule 8.04) that gives a pitcher 12 seconds to make a pitch from the time he has the ball with the batter in the box until he releases it. But it’s not enforced.

If the 20-second rule came into play, with approval from both MLB and the players’ union (which could argue hurrying a pitcher could cause more injuries), it would work only if consistently enforced, either with a clock behind the plate or held by the second-base umpire.

According to Fangraphs.com, among pitchers with at least 45 innings Santiago Casilla takes the second-longest time in the majors between pitches, 28.5 seconds. Matt Cain is the quickest Giant, 21.3. On the A’s, John Axford is the most deliberate, 26.9, and Kendall Graveman the most rapid, 20.5.

It would make sense if some relievers work more slowly than starters, especially in high-leverage situations. The quickest pitcher is starter Wade Miley (Mariners, Orioles), who takes just 17.7 between pitches.

It’s an idea that would be met with criticism, but one that could help put pace-of-game issues to rest.

John Shea is a San Francisco Chronicle staff writer. Email: jshea@sfchronicle.com Twitter: @JohnSheaHey