NEW YORK — The threat to opening day on March 31 appeared to intensify Thursday when the drawn-out talks to end Major League Baseball’s lockout ended just 15 minutes after they had resumed following a four-day break.

What was supposed to be the second day of spring training workouts instead was the 78th day of the second-longest work stoppage in baseball history. After just the sixth meeting on core economics since the lockout began on Dec. 2, the sides had differing interpretations of the brevity: The union didn’t read much into the short session, and management attributed the lack of length to having nothing to talk about.

While there is a session scheduled for Friday on non-core issues, there is no set date for the resumption of the main talks. The sides have about two weeks left to reach a deal that would allow sufficient spring training ahead of an on-time opening.

“I just hope something gets resolved quickly,” Yankees infielder DJ LeMahieu said before the meeting, just after working out with teammate Aaron Judge at a college field in Tampa, Florida. “Baseball becomes a business — it’s not as fun, but it’s something that definitely needs to happen.”