NEW YORK -- Baseball players and owners had a deal to expand active rosters from 25 to 26 players for most of the season, but the union backed away in the final stages of collective bargaining.

As part of the deal, the limit from Sept. 1 on would have been lowered from 40 players to 28.

"We thought we were going to make an agreement, had a tentative agreement," baseball commissioner Rob Manfred told The Associated Press on Friday, "but nothing's done until it's done."

Union head Tony Clark characterized the talks differently and said the parties could revisit the topic during the five-year contract they agreed to Wednesday.

"I don't know that there was an agreement to do it and that it came apart. There was a lot of dialogue over the course of this round where we were moving in a direction that we inevitably weren't able to agree to," he said. "It simply got to the point with all of the moving pieces that were part of the conversation during the course of the year that we lived to talk about it another day."

Rosters have long expanded for the season's final full month as minor league affiliates end their campaigns. The roster expansion gives managers the ability to make more frequent pitching changes in an attempt to gain favorable matchups.

Some managers and general managers have complained it doesn't make sense to play most of the season under one set of rules and then switch as pennant races heat up. While some teams add many players and a few reach the 40-man limit, others make relatively few call-ups.

"There were very mixed opinions on the club side, as well," Manfred said. "Maybe we were going too far, too fast."

Many players make their big league debuts in September, and the union has long been concerned about the loss of service time if the limit were to be lowered from 40.

"To reduce the roster to 28 people would jeopardize the ability for people to get their feet wet in the big leagues," Oakland catcher Stephen Vogt said in a text. "September is a great time for teams to teach the young guys how to act and be in the big leagues and get their feet wet in a comfortable environment."

Given the increasing importance of bullpens, some believe a 26th player likely would be an additional relief pitcher.

"I know there have been a lot of concerns from the other side related to just how it would work and how it might affect the games or the length of games," Clark said. "Trying to appreciate that extra player and who it may be is hard to predict based on whatever the organization philosophy is of any one team."

Management and the union released details of the deal Friday, an agreement that will extend the sport's labor peace to 26 years since the 1994-95 strike -- baseball's eighth work stoppage since 1972.

"We kept the game on the field," Manfred said. "We made an agreement within our current structure which I think shows that we have a durable structure. We moved some things our direction, and we moved some other things their direction."

The threshold for the luxury tax, known formally as the competitive balance tax, rises from $189 million this year to $195 million in 2017 to $210 million in the deal's final season. There are some rate increases and new surtaxes.

"The premise of the CBT altogether was a drag at the top to keep teams from running away from the group," Clark said.

Manfred added: "There's two dynamics around the threshold: stopping people from running away but also having them low enough that people can aspire to spend a little more to be a little more competitive."

Among the new details that emerged:

• The penalty for a second stimulant violation goes up from 25 to 50 games and for a third rises from 80 to 100. The penalty for a first violation remains follow-up testing.

• Random urine tests will increase from 3,200 to 4,800 in-season and from 350 to 1,550 in the offseason, ensuring at least one offseason test for all 40-man roster players. Random blood testing rises from 260 to 500 in-season and from 140 to 400 in the offseason.

• The number of teams disqualified from revenue sharing drops from 15 to 13. A person familiar with the details, speaking on condition of anonymity because no announcement was made, said Atlanta and Houston were the teams that became eligible.

• Major league players may not be traded during the final week of the regular season.

• The new All-Star bonus pool for the winning team is $640,000, which calculates to $20,000 per player.

• After fan and player voting, the final roster selections in each league (seven in NL and five in AL) will be made by the commissioner's office rather than the All-Star managers.

• While a team with a payroll $40 million or more above the luxury tax threshold would have its highest draft pick dropped 10 places, the top six selections are protected, and those teams, if penalized, would have their second pick dropped 10 slots.

• The commissioner may schedule regular-season games at ballparks other than the regular sites, and players would receive additional compensation.

• Players would receive $15,000 to $100,000 each for special events such as games in Mexico, Asia, Puerto Rico, the Dominican Republic and London.

• Signing bonuses of $10,000 or less do not count against a team's international signing bonus pool.

• Teams will increase their annual pension and medical benefits contribution to about $200 million.