By Keith Idec

An average of 659,000 viewers tuned in to Showtime’s live telecast Saturday of the highly entertaining Anthony Joshua-Wladimir Klitschko heavyweight title fight from London.

The average viewership, based on figures released by Nielsen Media Research on Monday, was the highest in Showtime’s history for a live boxing broadcast that began in the afternoon. The Joshua-Klitschko fight started just after 5 p.m. ET and 2 p.m. PT.

Nielsen is expected to release the peak viewership for Showtime’s telecast Tuesday. Initial numbers indicate, however, that Showtime’s average audience was 687,000 from 5:15-5:30 p.m. ET, when the pivotal fifth and sixth rounds took place.

Nielsen’s ratings for HBO’s delayed telecast, which aired at 11 p.m. ET/PT on Saturday, will be released Tuesday as well.

In the ring, Joshua-Klitschko, which drew a record crowd of roughly 90,000 to Wembley Stadium, delivered memorable drama after being billed as the biggest heavyweight fight since Lennox Lewis knocked out Mike Tyson in June 2002. England’s Joshua dropped Klitschko in the fifth round, but tired himself out while trying to finish the 41-year-old former champion in that round.

Joshua’s exhaustion enabled Klitschko to mount a riveting comeback. Klitschko dropped Joshua with a right hand in the sixth round, but Joshua also was able to withstand that severe trouble, despite that there was 1:53 to go in the sixth round when he went down.

The 27-year-old Joshua (19-0, 19 KOs) eventually got his legs back under him, got his second win and attacked Klitschko (64-5, 53 KOs) to start the 11th round. He dropped Klitschko twice more before referee David Fields stopped the bout at 2:25 of the 11th round, with a vulnerable Klitschko still standing.

There is an immediate rematch clause in their contract, but Klitschko said following his first knockout loss in 13 years that he’ll take his time in determining whether he’ll pursue a second fight against Joshua.

Showtime will replay the Joshua-Klitschko fight at 10 p.m. ET/PT on Monday on SHO Extreme.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.