St. Louis Cardinals manager Oliver Marmol and umpire C.B. Bucknor shook hands when lineup cards were exchanged before a game Monday in Jupiter, Florida, two days after Bucknor refused to and the manager said Bucknor "had no class."

"I was raised and brought up in this organization to do exactly what I did today," Marmol said. "You go to home plate. You hand the lineup card and you shake the hands of the four umpires who are running that game."

The bad blood dates back to a game last year when Bucknor ejected Marmol.

Bucknor declined to shake Marmol's hand Saturday, according to Marmol, and Major League Baseball is looking into that exchange. Marmol was upset by Bucknor's response at the time.

"I don't think he's good at his job, and it just shows a lack of class as a man," Marmol said after the game Saturday.

An MLB spokesperson told ESPN's Buster Olney on Sunday that "we are aware of Mr. Marmol's comments, and the matter is under review."

Bucknor and Marmol had a confrontation during an August 2022 game after a disputed strike call to Cardinals third baseman Nolan Arenado. Bucknor ejected Marmol, who emerged to argue -- and as the two yelled at each other, Marmol appeared to tell Bucknor that his time in the sport was done, and Bucknor yelled back that Marmol, relatively new to his position as St. Louis manager, had just gotten to the big leagues.

On Saturday, Marmol went to home plate for the exchange of lineup cards, and according to Marmol, Bucknor would not shake his hand. The other umpires -- Ron Kulpa, Angel Hernandez and Carlos Torres -- did shake Marmol's hand. According to Marmol, others apologized for Bucknor's refusal.

Bucknor, 60, has been a major league umpire since 1996. Marmol, 36, became the Cardinals' first-base coach in 2017 and was hired as St. Louis manager after the 2021 season.

Marmol's Cardinals defeated the New York Mets 12-7 on Monday.

The Associated Press contributed to this report.