PARADISE VALLEY, Ariz.—The head of the committee that developed Major League Baseball's plan to expand instant replay says he is optimistic the system will be in place this season, even though owners and unions for players and umpires have yet to approve.

Atlanta Braves President John Schuerholz said that because of the complexities, he expects the system will need three years of use to resolve problems that develop.

The plan would give managers the right to challenge most calls except balls and strikes, with one challenge allowed in the first six innings and two from the seventh inning on. A successful challenge would not count against the limits.

Schuerholz said he was uncertain whether owners would vote on the proposal during Thursday's meeting. Owners always could vote later by telephone.

Schuerholz expects the umpires' and players' union to go along with the plan.

"There's been a great deal of dialogue," he said, "and our anticipation is that both of our partners will be willing and ready to go forward."

The new executive director of the players' association, Tony Clark, also sounded optimistic about expansion of video review.

"It's been a challenge to try to navigate how best we do this without disrupting the game itself," Clark said in an interview with The Associates Press. 'Our guys are very concerned with making sure the game stays the same."

Speaking Wednesday at the hotel where the owners were attending a quarterly meeting, Schuerholz said the replay expansion should enhance the sport.

"We are in uncharted waters," he said. "But behind all of this and buttressing all of this we should remember that in the doing of this, managers will be given an opportunity that they've never had in the history of the game, and that is to challenge a play and perhaps have it reversed, and perhaps have that reversal benefit their team, and win a game that might win a division that might get them into a playoff. And who knows from there?"

Schuerholz has been joined on the replay committee by former managers Joe Torre and Tony La Russa, both current MLB executives. Scheurholz agreed with Clark that there will be adjustments after the system is put in place.

"We feel like we've worked through this process in as much detail as possible," Schuerholz said. "We realize the further we get in, the complexities involved. And that's what's taken time. There will probably be complexities that show themselves that we might not have dealt with. But as I keep telling everyone, this is a three-year rollout. ... This is uncharted territory for us—and for the industry and for the managers and for the replay officials and for the umpires. For everyone."

Clark said he knows that "there are going to be challenges, and that despite wanting to fix everything so that it works perfectly from day one, that we may have to adjust some things as we go on."

It also was uncertain whether the owners would vote this week on a proposal to ban home-plate collisions. That rule also would be subject to approval by the players' union if it is to be implemented this season. MLB can implement it unilaterally in 2015.

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AP Sports Writer Ronald Blum in New York contributed to this report.