Celebrations for Puerto Rico at the World Baseball Classic turned sour when pitcher Edwin Diaz hurt his knee after their victory against the Dominican Republic.

The New York Mets closer – widely considered to be the best in the game – eliminated the favourites for the competition as he struck out Teoscar Hernandez to complete a 5-2 victory.

In the ensuing celebrations, the players were jumping in a huddle before stopping once it became apparent that Diaz was injured.

His brother, Cincinnati Reds reliever Alexis Diaz, was in tears as medics attended to him, helping the 28-year-old from the field.

According to ESPN, the 28-year-old will undergo an MRI on Thursday, with sources fearing "the injury could keep Díaz out for a significant period".

"I didn't see it right away," Puerto Rico manager Yadier Molina said. "I was hugging our coaches in the dugout, and when we looked up, Edwin was on the ground.

"I didn't know. I didn't know how to act, I didn't know what to say. It caught me by surprise. It sucks. When you see a guy that works so hard like Edwin, when you see him on the ground like that, it's just sad."

Center fielder Enrique Hernandez added: "It wasn't pretty much until we got to the infield dirt that we realised something had gone wrong.

"At the moment we didn't know who it was. When we got there, that's when we realised who it was. Obviously, aside from being the best closer in the game right now, and being a huge part of this team, [Diaz] is one of the glue guys in that clubhouse."