Rivera suffered a torn anterior cruciate ligament in his right knee during batting practice prior to Thursday's game in Kansas City, Mo. He was taken from the field on a cart, but by Friday he was saying to not count him out.
"I'm coming back. Write it down in big letters. I'm not going out like this," Rivera said Friday.
Earlier he sent a post to his Twitter account thanking fans and promising, "I will be ok. I will be back."
Rivera, 42, was in the outfield running down fly balls while his teammates were taking turns in the batting cage prior to New York's game, something he has done throughout his career.
He jumped near the wall in an attempt to catch a ball and when he came down his right knee gave way. He fell to the ground in obvious pain and was taken to a hospital where doctors confirmed the torn ACL diagnosis.
Rivera owns the major league record with 608 saves. He has a 76-58 record with a 2.21 earned run average and 1,119 strikeouts over 18 seasons -- all with the Yankees.