Eimantas Stanionis' promoter, Richard Schaefer, told ESPN the fighter had an emergency appendectomy Friday in Lithuania, postponing the March 18 welterweight fight vs. Vergil Ortiz in the Dallas-Fort Worth area.
Stanionis, 28, was released from the hospital Saturday.
"We communicated to Golden Boy, who is going to look at available dates for the second half of April," Schaefer said. "He needs to follow doctor's orders and he will be ready to go.
"He was sparring, he's been training really hard, and he felt some pain. Went to go see the doctor and he needed immediate surgery. He was upset."
Oritz's promoter, Golden Boy, won the rights to the WBA "regular" welterweight title fight at last month's purse bid with a commitment of $2.3 million and will stream the fight on DAZN.
Golden Boy will kick in additional money to make Ortiz, who is a far bigger star than Stanionis in the U.S., whole. The Lithuanian boxer won the secondary title with a split-decision victory over Radzhab Butaev in April and is entitled to 75% of the winning bid, while Ortiz will earn much more than the $575,000 he's set to make via the purse bid.
The bout shapes up as a coin-flip matchup between two pressure fighters in one of boxing's best weight classes.
Ortiz (19-0, 19 KOs) is rated No. 4 by ESPN at welterweight. The 24-year-old broke through last year with a pair of stoppage wins over Maurice Hooker and Egidijus Kavaliauskas. Ortiz was set to fight Michael McKinson in March, but the fight was postponed after Ortiz was hospitalized with rhabdomyolysis.
Rhabdomyolysis is a breakdown of muscle tissue that releases the damaging protein myoglobin into the blood, which can lead to kidney damage. Ortiz went on to score a ninth-round TKO of McKinson in August and will now step way up in class.
Stanionis (14-0, 9 KOs) is ESPN's No. 6 boxer at 147 pounds. He also owns a win over Thomas Dulorme.