This is goodbye for Michael Phelps. The most decorated athlete in Olympic history has one more race before retirement.

What time does Michael Phelps swim tonight (Saturday, August 13, 2016)?

What: 4x100m medley relay

When: 9:04 p.m. central time/10:04 p.m. eastern

TV Channel: NBC

Stream: NBCOlympics.com

His shot at a 28th medal comes Saturday in the final slate of swimming at the Rio de Janeiro Games, where Usain Bolt thrilled the crowd at Olympic Stadium in his first appearance of the games and Rafael Nadal’s bid for an unprecedented second Olympic singles gold medal ended with a thrill-a-minute semifinal loss to Juan Martin del Potro.

With four gold medals at these games and 22 for his career, Phelps needs some help from his teammates to win another — he leads off with the butterfly leg of the 400 medley relay.

The Associated Press contributed to this report.