- Michael Phelps is expected to end his Olympic career in the 4x100-meter medley relay
- Jamaican sprinter Usain Bolt begins his defense of his 100-meter Olympic crown
- In basketball, Lithuania takes on the United States and Russia faces off with Spain
- After a controversial week, women's badminton ends with the gold-medal match
Track and field competition revs up on Saturday, but not before swimmers -- among them, the most decorated Olympian of all time -- make one final splash in the pool. Here are five things to look for Saturday at the 2012 London Games:
1) Swimming: Phelps to cap historic Olympic career
Sometime around 8:30 p.m. in London, Michael Phelps' Olympic career is expected to end with the men's 4x100-meter medley relay. He'll likely finish his career with 22 medals, 17 or 18 of them gold, after winning the 100-meter butterfly on Friday. Other swimming finals set for Saturday are the women's 50-meter freestyle, the women's 4x100-meter medley relay and the men's 1,500-meter freestyle.
Swimming begins at 7:30 p.m. London time (2:30 p.m. ET) and could wrap up an hour later.
2) Track and field: World's fastest men and women burst out of the blocks
You remember Usain Bolt, don't you? Well, in the past year he's been overshadowed by teammate Yohan Blake, who won the world championship (after Bolt false started) and also beat the defending Olympic champ and preening world record holder in the Jamaican trials in both the 100 meters and 200 meters. After the men run heats in the morning, the women will run the 100-meter final on Saturday night. The top qualifiers so far are American Carmelita Jeter and Jamaicans Shelly-Ann Fraser-Pryce, Kerron Stewart and Veronica Campbell-Brown.
And for those who prefer a slower pace, the men's 20-kilometer race walk final will roll in late in the afternoon.
Track and field competition starts at 10 a.m. (5 a.m. ET) and continues much of the day, capped by the women's sprint final just before 10 p.m.
3) Men's basketball: Can Lithuania contain Team USA?
Lithuania will try to keep the United States under 150 points on the basketball court -- and, if they have their way, end the modern-day Dream Team's undefeated run so far this Olympics. The Americans scored an Olympic-record 156 against Nigeria on Thursday, on the same day the Lithuanians lost to France 82-74.
Linas Kleiza, who plays in the NBA for the Toronto Raptors, leads Lithuania (1-2) in scoring. But a matchup earlier Saturday between two undefeated teams, Russia and Spain, is expected to be more competitive.
The Russia-Spain game tips off at 11:15 a.m. (6:15 a.m. ET), and the U.S.-Lithuania tilt is at 2:30 p.m. (9:30 a.m. ET).
4) Badminton: After disqualifications, competition comes to close
Women's doubles badminton comes to an end with a Chinese duo playing for the gold medal -- but not Yu Yang and Wang Xiaoli. They were among eight players booted from the tournament this week for trying to lose their match. Four of the players that benefited from the dismissals, Canadians Michelle Li and Alex Bruce and Russians Nina Vislova and Valeria Sorokina, will play for bronze, while the gold medal contest pits China's Yunlei Zhao and Qing Tian against Japan's Mizuki Fujii and Reika Kakiiwa.
Medals also will be awarded Saturday in the women's singles competition, where three of the four contenders are from China.
The bronze medal women's double match will be at 10:30 a.m. (5:30 a.m. ET), with the gold medal contest at 3:45 p.m. (10:45 a.m.).
5) Tennis: Serena and Sharapova square off on Centre Court
America's Serena Williams and Russia's Maria Sharapova are no strangers to the All-England Club, with the former boasting five Wimbledon titles and the latter one in their careers. On Saturday, the two battle on the court's famed grass for Olympic gold. They will be followed on Centre Court by the men's gold medal doubles match between twin brothers Mike and Bob Bryan of the United States and Frenchmen Michael Llodra and Jo-Wilfriend Tsonga. Mike Bryan better hope it's a quick contest: He's scheduled to play in a mixed doubles semifinals match with Lisa Raymond just 30 minutes after his other contest is set to end.
The gold medal women's singles match is scheduled to start around 2 p.m. (9 a.m.), followed by other contests.