Rob Manfred envisions more experiments with speed-up rules, such as limiting pitching changes and trips to the mound, or requiring each pitcher to face multiple batters.

Speaking at the Sports Diversity & Inclusion Symposium on Wednesday, the new baseball commissioner said he doesn't see any need to expand the designated hitter to the National League. Manfred also expects teams and the players' association to discuss possible changes to September callups during collective bargaining for a contract that starts before the 2017 season.

Concerned the average time of nine-inning games climbed to 3 hours, 2 minutes in 2014, owners and players agreed to install clocks to time between-innings breaks and pitching changes, and to require hitters to keep at least one foot in the batter's box in many instances. The average has dropped to 2:56 this season.

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More radical rules, such as a 20-second pitch clock, were used in the high minor leagues.

"You will see a continuing evolution of our rules in order to speed the game," Manfred said to the audience at Citi Field. "Things like visits to the mound, both catcher and manager visits. It's always been astounding to me exactly what wisdom is imparted in those visits, with all due respect to the great managers."

Playing rules can be changed without the union's consent only with one year of advance notice. MLB has preferred to make alterations players agree to.

"We've actually talked about more fundamental changes," Manfred said. "Pitching changes are a huge part of the length of the game -- limiting the number or requiring a pitcher to pitch to at least two batters, something like that."

Manfred said he wasn't sure any players were fined for violating the speed-up rules this year. He also said he didn't think every speed-up idea MLB experiments with will be adopted.

Manfred said he understood why the Red Sox did not interview minority candidates when Boston owner John Henry hired Dave Dombrowski as president of baseball operations in August, two weeks after Dombrowski was fired by Detroit. In 1999, then Commissioner Bud Selig started requiring teams to interview minority candidates for openings at general manager, assistant GM, manager, director of player development and director of scouting.

"He had worked for John Henry before. There was a personal relationship there. The Red Sox were not engaged in a search," Manfred said. "Dave became available during the season. It was a fait accompli as to what was going to happen, and I recognized the reality of that situation and let the hiring go forward. I see it as a unique set of circumstances."

Manfred noted that nine of the 36 first-round draft picks this year were African-American, a sign baseball's efforts were "starting to bear fruit." The percentage of African-Americans in the major leagues has been cut in half since peaking at about 18 percent at times from the mid-1970s to mid-1980s.

Since succeeding Selig in January, Manfred has made youth baseball a priority.

"We had underinvested in what is an extraordinarily competitive market -- that is, for youth sports. Kids have far more choices today that we did," he said. "I think that it is very important to us that we attract world-class athletes. And in order to attract the best athletes and keep enough of them in the game to make our product compelling, you have to have play in all segments of our society, and as a result, we have to place a special focus on underserved areas."

On other topics, Manfred said of reconsidering September roster expansion to 40: "It was a topic in the last round of bargaining. Because we didn't make a deal, I don't think anybody really realizes that it was extensively discussed, and I suspect it will be a topic of discussion this time around."

And on Alex Rodriguez's return from his 2014 drug suspension, Manfred said: "He's done a really good job. He's played very well. He's gone out of his way to try to do the right thing with respect to off-field matters, and I couldn't be happier for him."