LONDON (CNN) -

Swimming and gymnastics once again take center -- or is it centre? -- stage Thursday with a head-to-head swimming battle and the women's individual all-around medals at stake. Here's what to look for in that and other top events:

1) Gymnastics: A new queen

With world champion Jordyn Wieber excluded from the women's individual all-around competition because she finished fourth, but third among Americans, in a qualifying system that allows only two people per nation, the United States still has the favorite for gold. Gabby Douglas led the Americans to the team title when she finished second in the vault, third on the floor, fourth on the balance beam and sixth on the uneven bars. Viktoria Komova of Russia was the top scorer in the qualifying round. They will be matched against each other in first rotation along with Aly Raisman of the United States and Aliya Mustafina of Russia.

The individual all-around starts at 11:30 a.m. London time (6:30 a.m. ET)

2) Swimming: The second big showdown

Michael Phelps, the most famous U.S. swimmer ever, will be in Lane 3. Ryan Lochte, who was supposed to be one of the big winners in these Games, will be in Lane 4. It's the Showdown, part II. On Saturday, Lochte won the first head-to-head meeting between the two stars, though Phelps didn't even medal in the 400-meter individual medley. But Lochte also swims in the 200-meter backstroke final just a half hour before the 200-meter individual medley. Should Phelps win the event, he would be first male swimmer to accomplish the feat in three consecutive Olympics.

The 200-meter individual medley final starts at 8:19 p.m. London time (3:19 p.m. ET)

3) Equestrian: Ann Romney's horse set to take part in the Games

Ann Romney, wife of the soon-to-be Republican nominee, will be on hand to see her horse Rafalca compete in dressage. Mitt Romney will be traveling from Boston to Colorado for campaign events. Commentators seem to think the Republican candidate has a better chance in his race than Rafalca, ridden by Jan Ebeling, has in her event.

The individual dressage competition starts at 11 a.m. London time (6 a.m. ET) while Ebeling is scheduled to ride Rafalca about an hour later.

4) Volleyball: Battle of unbeatens

Men's world No.1 Brazil will face the United States in a rematch of the Beijing Games final, which the U.S. won in a thrilling four sets. Each side has won its first two matches without losing a set.

The match takes place at 8 p.m. London time (3 p.m. ET)

5) Table Tennis: They don't play to lose

While controversy may have hit the badminton courts, table tennis has rolled on. But world champ Zhang Jike has not been without his own controversy in the past. In 2004 he was bumped from the Chinese national team for violating team rules. He came back with a new attitude and now has a chance to become the fourth male grand slam winner. He plays Dimitrij Ovtcharov of Germany in one semifinal while countryman Wang Hao plays Chuang Chih-Yuan of Taiwan. The winners meet later in the day for the gold medal.

Table tennis semifinals begin at 10 a.m. London time (5 a.m. ET).