IRVING, Texas — On Thursday morning, many baseball fans woke up to find their favorite sport in a very different state.

At 12:01 a.m. Eastern on Thursday, immediately after the collective bargaining agreement between the owners of Major League Baseball’s 30 clubs and the players expired and no new deal was reached, the league instituted a lockout. The move began the ninth work stoppage in M.L.B. history — and first in 26 years — bringing the sport to a virtual standstill.

Immediately, all of the M.L.B.’s websites, including MLB.com and the various team sites, had been scrubbed of mentions of current players. Citing the lockout and labor law, M.L.B. removed players’ photos from their statistics pages and replaced them all with the same generic silhouette. And the dominant presence on the sites was an 800-word letter that M.L.B. Commissioner Rob Manfred wrote to fans explaining the league’s decision to enact what he called a “defensive lockout.”

Nine hours later, Manfred sat in front of TV cameras at Globe Life Field, the Arlington, Texas, home of the Rangers, to further explain why he thought it had come to this.

“It’s not a good thing for the sport,” he said of a lockout, even one that comes during the off-season. “It’s not something that we undertake lightly. We understand it’s bad for our business. We took it out of a desire to drive the process forward to an agreement now.”

Players, though, will not be pushed around, said Tony Clark, the executive director of their union. When he and Bruce Meyer, the union’s lead negotiator, met with reporters not long after Manfred spoke, Clark said M.L.B. had referenced a possible lockout “on more than one occasion” during negotiations should a new agreement not be struck by 11:59 p.m. Eastern on Wednesday.

Much like Manfred said about his own side (“We came to Texas to make a deal”), Clark said his side had hoped to reach a new agreement this week while in the Dallas area, where the union held its annual executive board meetings at a hotel. (M.L.B. officials and a handful of key club owners came to Texas this week to negotiate directly with the union and players.) And much like Manfred said about the union, Clark said it seemed like M.L.B. wasn’t trying hard enough to strike a pact.

“From the outset, it seems as if the league has been more interested in the appearance of bargaining than bargaining itself,” said Clark, who then stressed that M.L.B. wasn’t required to impose a lockout. He added, “And contrary to the statement that imposing a lockout would be helpful in bringing negotiations to a conclusion, players consider it unnecessary and provocative. This lockout won’t pressure or intimidate players into a deal that they don’t believe is fair.”

Manfred said he had the support of all 30 clubs to enact the lockout, which freezes all contact with players and transactions, from free-agent signings to trades. He added, citing the National Labor Relations Act, “We didn’t feel that sense of pressure from the other side during the course of this week, and the only tool available to you under the Act is to apply economic leverage.”

Manfred repeatedly cited the 1994-95 strike — the last work stoppage in baseball to cost regular-season games (over 900 in all) — as a lesson for now. When the C.B.A. expired then, the 1994 season began without a new agreement. Players went on strike in August as M.L.B. sought to add a salary cap. The union successfully avoided the institution of a cap, but the 1994 World Series was canceled and the strike didn’t end until April 1995, with a legal battle playing out in public.

“We made the mistake of playing without a collective bargaining agreement in 1994, and it cost our fans and our clubs dearly,” Manfred said. “We will not make that same mistake again.”

This expired five-year C.B.A. was viewed as having further tilted the balance in the owners’ favor. Top players have been awarded record contracts in recent years — and weeks — but the average major-league salary had either remained flat (around $4 million) or dropped. Younger players, who are cheaper, have been relied upon more by teams. And the union has been bothered by the clubs that manipulate players’ ability to accrue service time and the clubs that receive tens of millions in revenue sharing from their counterparts yet purposefully don’t compete for playoff spots.

Players have wanted a series of improvements: getting younger players compensated sooner, allowing players to reach salary arbitration and free agency sooner, raising luxury tax thresholds (from $210 million to $245 million), reducing revenue sharing by $100 million, creating ways that could curb service time manipulation, and forcing teams to be more competitive through a handful of measures, including changes to the amateur draft.

Owners, though, believe baseball players have the best deal in professional sports. Among their proposals, some of which have been rejected by the union: an N.B.A.-style lottery format for the first three picks in the draft that could help prevent so-called tanking, a club payroll floor ($100 million) along with a lower luxury tax threshold ($180 million) — or more modest luxury tax threshold increases (starting with $214 million) without a floor but with steeper rates for going over, overhauling the salary arbitration system, smaller increases to league minimum salaries and making free agency based on age (29.5) instead of service time (six years).

In his letter, Manfred characterized the union’s requests as “collectively the most extreme set of proposals in their history.”

He added at his news conference on Thursday: “We already have teams in smaller markets that struggle to compete. Shortening the period of time that they control players makes it even harder for them to compete. It’s also bad for fans in those markets. The most negative reaction we have is when a player leaves via free agency. We don’t see that making it available earlier as a positive. Taking $100 million away from teams that are already struggling to put a competitive product on the field, I don’t see how that’s helpful.”

The union fired back. Meyer said the proposal to allow players to reach salary arbitration eligibility at two years of service time, not three, wasn’t “radical” because it had been like that for about 15 years before. (In 1987, eligibility was narrowed from three years to two.) And he said combating service time manipulation also wasn’t extreme.

“We believe that the radical proposals have come from the other side, not from us,” said Meyer, contending that M.L.B.’s proposals for arbitration and free agency would be worse for players. He said the union’s proposed changes were meant to improve the competition among teams, including measures to help small-market teams.

“The league has consistently said on revenue sharing they will not change it, period,” Meyer added later. “So that’s just an example of what we’ve been saying that the league really hasn’t been prepared to negotiate. It’s a whole list of topics that they told us they will not negotiate.”

Clark said the union made “proposals that moved significantly” toward M.L.B. on “a number of key economic issues.” (The union, for example, offered on Tuesday a version of expanded playoffs, which the owners have wanted, and allowing advertising patches on jerseys, which would net more revenue.) He said M.L.B. “refused repeatedly” to make counter offers in Dallas on any of the union’s core economic issues.

Manfred bristled at the notion that the league hadn’t made enough proposals. He said, for example, that M.L.B. made an offer on Wednesday morning — the day of the C.B.A. expiration — that “if it had been accepted, I believe would have provided a pretty clear path to make an agreement.”

Meyer said the union didn’t consider that a proposal because it came with binding stipulations that they drop a number of key demands before seeing the rest of M.L.B.’s offer.

“We proposed the elimination of draft-choice compensation,” Manfred said of one of M.L.B.’s offers. “This industry had a strike over that issue in 1985. That is a major concession that has been the source of friction as to how the free agency system has operated. We have made concessions.”

If it would lead to a fair agreement, Manfred said M.L.B. was prepared to make more concessions. Added Meyer, “We are and have always been ready to negotiate on every issue. We have not drawn any hard lines in the sand.”

Both sides said no further meetings were planned for the moment but they had agreed to keep negotiating. There is time to reach an agreement without jeopardizing games, but the clock is ticking to do a lot of heavy lifting. Spring training is scheduled to start in mid February and opening day is slated for March 31.

Asked for his drop-dead deadline to avoid costing regular-season games, Manfred said it was “not productive” to speculate at this point.

“As we sit here on Dec. 2, I’m not going to give you a date or a deadline for games to be missed,” Clark added. “Our hope is to get a deal done such that sooner rather than later the positive nature of what is going on in our game is garnering more attention and headlines than what is happening right now.”