Nationals starting pitcher Doug Fister is known as a quick worker on the mound. (Jonathan Newton/The Washington Post)

Last fall in the Salt River Rafters’ minor league home park in Scottsdale, Ariz., Major League Baseball saw its future — if it is very, very lucky.

Fifty years ago, the average time of an MLB game was 2 hours 35 minutes. Last year, it was 3:02, the worst ever. At Rafters’ home games in the Arizona Fall League, with five “timers” on the park walls and experimental rules that were tighter than those that will be used in the majors to pick up “pace” this season, the average time was 2:39.

To those such as Joe Torre and Tony LaRussa who watched with excitement, it was like traveling in a baseball time machine. Time of game in 1954: 2:30. In 1984: 2:40. That’s where the sport should be and can be again — if players let it happen.

The most important change in baseball in 30 years — a change in the feel and experience of the game itself, not in issues surrounding the sport — has just begun.

It’ll take years, maybe a decade, to find out if MLB can crack its pace of game problem. But players, and their union, for the first time are acting like full partners in their sport, agreeing to help in a get-a-move-on-it campaign this year. Is it really true that “where there’s a will, there’s a way?” Baseball better hope so.

Perhaps nothing is more important to the game’s mass appeal in the 21st century than eradicating that hideous number “3:02.” Playoff games averaged 31/2 hours. The Nationals needed 6:23 to play 18 innings in Game 2 of the NLDS. The Orioles needed 4:17 for nine innings in Game 2 of the ALCS. Many of us have screamed for years. But now is crunch time.

Baseball finally has a model. The Arizona Fall League, which John Schuerholz, the chairman of the Pace of Game Committee, calls “our laboratory,” has provided it. The gap between lab results and MLB rules now used in spring training and the 2015 season are significant. But, in time, they may be bridgeable.

MLB has identified the biggest of all time wasters: long breaks between innings. For years, this was blamed on a necessary evil: more commercials to make more money. But that’s proved to be only partly true. Games can average 45 squandered seconds per half inning after TV returns to the air. Just bad habits.

So this year, every park will have a timer. “We don’t call it a ‘clock,’” says Schuerholz wryly. After the last out, the leadoff batter for the next inning has 2 minutes 5 seconds to step into the box. The pitcher must throw by 2:25. Don’t be fooled. This is mostly cosmetic. It may save a couple of minutes. But it’s a Trojan Horse. That 2:25 still allows sleepwalking — I’ve timed it in regular season, playoff and this year’s spring training games.

But once a timer is accepted, then you can gradually find out how much that 2:25 can be tightened — to the game’s advantage and no one’s harm.

For example, at Salt River’s park, willing minor leaguers played by lab-rat rules that worked. Hitters had 1 minute 45 seconds to get in the box, not 2:05, and hurlers 2:05 to pitch, not 2:25. Penalties for failure: “Strike one!” or “Ball one.” Relievers, waved from the bullpen, had the same 2:05 time limit.

Just three penalty “balls” were called all season. But that extra 20 seconds saved by hustle between innings cuts six more minutes. And it’s all in dead times when nobody, in the park or on TV, even notices. The game’s flow isn’t damaged.

Because most MLB teams, such as the Nationals, have 90 seconds of commercials, a 2:05 rule could work in theory. Or 2:15. Whatever players will bear to help their game.

“Rafter Rules” also had a wonderful law: Mound conferences of any kind, even catchers visiting pitchers, were limited to three per team. That took 130 years?

Games at Salt River also used the new rules the whole AFL employed. Most important: With the bases empty, the batter couldn’t step out of the box between pitches (unless he had swung) and the pitcher had to throw within 12 seconds of receiving the ball from the catcher. The majors now have slightly gentler versions of those rules this year. Really, the Major League Baseball Players Association hasn’t given up any ground on what might be considered workplace rules. They’re just embracing what’s on the books.

Now, we’ll see if players act like partners. A true culture change is needed. That’s hard. Journalists don’t like deadlines changes that force them to write faster. And slow boats such as David Ortiz don’t like to alter habits, including elaborate out-of-box rituals on every pitch.

That’s how Ortiz has earned $150 million. Honestly, who wants to change patterns adopted as a child? Yet, Ortiz has been heard in spring training muttering, “Stay in the box,” even in batting practice. He and others are cracking bad habits. That’ll take years. Wish ’em luck. The sport deeply appreciates their effort.

“Pace of game is a tough issue because it is nebulous,” Schuerholz said. “Part of it can be measured. A lot can’t. It’s about having a brisk, sharp feel. You want to keep the flow of the game but reduce the amount of down time.

“We’re encouraged that our partners [in the MLBPA] are interested in this,” Schuerholz said. “Some will be recalcitrant. A couple have been pretty vociferous. That’s expected. We have to re-educate. And that can take years.”

Class AA and AAA ball now have a form of the AFL rules.

“Each year [as players turn over], we’ll change some bad habits,” Schuerholz said.

“This accommodation and coddling of young star players starts in high school, travel teams and college with coaches and parents,” said Schuerholz, adding sardonically that, to beat the 2:25 clock, some players are trimming the “grand and traditional ‘walk-up song’ that has been part of our game for so long.”

Can big leaguers adapt behavior, especially in vital games, if motivated? Oh, yes. In the postseason, commercial breaks take 2:30, not 1:30. Such dead time kills ratings. So MLB, TV and the union all agree when the red light comes back on in October, everybody has to be ready — instantly.

Suddenly that usual 30-to-60-second yawning gap between return-to-air and first pitch disappears! In Game 1 of the NLDS between the Nationals and Giants, the first pitch of each inning was thrown an average of 12 seconds after Fox came back live! Craig Stammen needed one second. Stephen Strasburg chucked a pitch two seconds after a break.

Baseball isn’t slow. It wasn’t for generations. But many of today’s players are. That may be changing, helped by a pace of game shove. When players accept their responsibilities, as well as their cash, the sport’s biggest flaw will disappear.

Quickly.