American depth, Russia’s stars and more that we learned on Day 1 of women’s gymnastics

Women's gymnastics started on Sunday, and as always with gymnastics, there were surprises. The biggest shock of the day is that Gabby Douglas and Aly Raisman will represent the U.S. in all-around, leaving Jordyn Wieber out. What else did we find out?

The Americans are not invincible: Through the first rotations, the Americans were almost robotic in their perfection. They averaged 15.489 per routine on vault and uneven bars, but started to slip with little errors on beam. On the floor exercise, they made much bigger errors, with three gymnasts stepping out of bounds. Though finishing the day in the lead, they were not perfect.

[ Related: Weiber's pain is Raisman's gain ]

But their depth is unmatched: We shouldn't be surprised by Aly Raisman and Gabby Douglas edging out Jordyn Wieber for the spot in the all-around. It's not that Wieber had a bad day; it's that the U.S. has many good gymnasts who push each other. They finished 2-3-4 overall. Besides Russia, no other team had even two gymnasts in the top 10.

Russia is hot on America's heels

: If the U.S. hits every routine, they will win. However, if they stumble, the Russians will be there to take over. With high scores on floor and vault, plus all-around contenders Viktoria Komova and Aliya Mustafina, the Russians are a gold-medal threat.

The gymnastics federation has some unforgiving rules: Only two gymnasts per country can compete in the all-around and event finals. In the team final, three gymnasts per apparatus perform and every score counts. The rules both keep the best from competing and don't allow for any errors.

China's powerful 2008 will not be repeated: With the home crowd on its side, China won a team medal in 2008. Since then, injuries and age took their toll. It took a distant third behind the U.S. and Russia.

What's next: On Tuesday, the American women will attempt to win the first U.S. team gold since 1996. Thursday, Raisman and Douglas will attempt to keep the U.S. streak of winning the all-around going. A week from today, the event finals begin. Four women will represent the U.S. on individual events:

Vault: McKayla Maroney

Uneven bars: Gabby Douglas

Balance beam: Gabby Douglas, Aly Raisman

Floor exercise: Aly Raisman, Jordyn Wieber

The U.S. could walk away from 2012 women's gymnastics with as many as eight medals.

Related Olympics video on Yahoo! Sports:

More London Olympics content on Yahoo! Sports:
• Why do swimmers spit water all the time?
• Funny Lochte-Phelps video might be best of the 'Call Me Maybe' parody genre
• Kimberly Rhode: 1st American to medal in 5 straight Olympics