Major League Baseball’s latest proposal to its union for starting the pandemic-delayed season improved its previous offers but failed to meet the players’ demands of full, prorated salaries for 2020 — which means it probably did little to slow the sport’s descent toward a default scenario of a late-summer mini-season of 48 to 54 games.

MLB’s proposal, delivered to union negotiators Friday, called for a 72-game season starting July 14 in which players would be guaranteed 70 percent of their prorated salaries, according to a person familiar with the talks. That figure would rise to 83 percent, including a bonus pool, if the 16-team, expanded postseason is completed.

Commissioner Rob Manfred, in a television interview Wednesday, predicted MLB’s offer would represent “another significant move in the players’ direction in terms of the salary issue.” However, union leaders have been adamant that players would not accept additional pay cuts beyond the one agreed to in March — which called for them to earn prorated shares of their 2020 salaries based on the number of games played — and are expected to reject MLB’s latest offer.

While the union still could come back with a new counterproposal, it almost certainly would fall short of the owners’ demands for further economic concessions in the form of salary cuts — which they say they need for a season expected to be played mostly or entirely without fans.

Baseball has been effectively shut down by the novel coronavirus pandemic since March 12, when spring training games were halted. MLB and the union have been trading proposals for a truncated season since late May.

The union’s most recent offer, made Tuesday, proposed an 89-game regular season running from July 11 to October 10 and a 16-team postseason, with players paid full prorated shares of their salaries. That proposal would result in total salaries for players of around $2 billion in 2020, while MLB’s various proposals have ranged from around $1.2 billion in earlier offers to $1.5 billion in the most recent one.

The seemingly unbridgeable philosophical differences over whether players should accept additional pay cuts makes it increasingly likely baseball resorts to the default option.

In the absence of a deal, the March agreement gives Manfred the power to implement a schedule of his choosing, with as many games as owners are willing to pay players at full prorate — which is expected to be in the 48 to 54 range. That season probably would begin in the second half of July, preceded by a second spring training of about three weeks.

“We’re going to play baseball in 2020, 100 percent,” Manfred said on ESPN on Wednesday.

The regular season probably would conclude in September, with the World Series concluding by the end of October, as MLB fears losing its lucrative postseason to a second wave of the coronavirus in the fall.

The union could challenge MLB’s right to set those terms, on the basis of a clause in the March agreement calling on baseball to make a “good faith” effort to play as many games as possible. The union also probably would withdraw its support, contained in its recent proposals, for an expanded, 16-team postseason — potentially denying MLB the extra revenue.

While there is not known to be a hard deadline for a plan to start the season, MLB told the union it would need an agreement by Sunday to make its 72-game proposal work.

The sides also have yet to agree on health and safety protocols for playing amid a pandemic, despite a productive back-and-forth on those issues. If anything, the degree of difficulty has only climbed recently, with spikes in case numbers reported in states including Arizona, Florida and Texas.

Under baseball’s latest proposal, any player who felt uncomfortable playing amid the pandemic could opt out, but only those deemed high risk — as in the case of a player with a medical condition that leaves him susceptible to the coronavirus — would be paid and accrue service time toward salary arbitration and free agency eligibility.

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