Vicky Opitz promised her partner, Kerry Simmonds, at least one thing: They won't crash.

The two are world-champion rowers, world-record holders, and with any luck, future Olympians. And when they dip their oars in the Schuylkill early Saturday morning, they'll be something else, too: rookies.

Opitz and Simmonds, who usually row in the eight, will compete together as a pair for the first time at the Head of the Schuylkill Regatta.

"I know the Schuylkill pretty well," Opitz said. "I'm definitely familiar with the twists and turns, and which bridges to avoid getting too close to."

They are among more than 1,500 boats scheduled to participate in the two-day regatta this weekend. Organizes expect entrants from 24 states and six countries. Saturday's races feature college and open competition, while Sunday is set aside mostly for high school crews.

The regatta will conclude a remarkable racing season for Opitz, 25, and Simmonds, 24.

As members of the U.S. national team eight this summer, they set a world record at the World Rowing Cup and won gold at the World Rowing Championships.

Their experience Saturday will be a completely different beast.

Simmonds has never rowed on the Schuylkill. Opitz, a former member of Philadelphia's Vesper Boat Club, has competed at the Head of the Schuylkill twice. But neither has spent any time practicing together as a pair, which calls for a different, more technical approach.

The two planned to come down from Princeton, where the national team trains, to attend the regatta as spectators. Opitz thought it would be fun, and a good test of their fitness, to compete instead.

Simmonds will sit in the front of the boat and handle the steering, something they don't usually have to worry about on the eight, where the coxswain guides the rudder.

"She'll just tell me how to steer it. I'll just listen to her the whole time," Simmonds said. "I don't think I'd be so willing to do this if I didn't have someone who did this quite a bit."

Both have proved to be quick studies.

Their eight this summer had just one holdover from the gold-medal winning crew London Olympics. Even their coach didn't know what to expect.

Midway through their race in Lucerne, Switzerland, at the World Rowing Cup in August, their coxswain shouted that they were on world-record pace. Opitz and Simmonds could hardly believe it.

"In the heat of the moment you're not really thinking about numbers," Opitz said. "You're thinking, when is this going to be over? It's so painful."

They validated their performance by following it up with a gold at the World Rowing Championships in South Korea in August. It's a long way to the Rio Olympics in 2016, but both Simmonds and Opitz hope to be there.

And if they have to get there as a pair, that's fine, too.

"Honestly," Opitz said. "I will take whatever boat I can."

Head of the Schuylkill Regatta

Saturday and Sunday on the Schuylkill.

The Head of the Schuylkill Regatta is a "head race," an expression that comes from England. The winner received the title of Head of the River.

Boats are started sequentially and race against the clock. The 2.5-mile race begins above Strawberry Mansion Bridge, just north of where Kelly Drive intersects Hunting Park Avenue, and ends below the Girard Avenue Bridge, just above Boathouse Row.

College crews will race on Saturday along with the majority of elite and masters rowers.

Sunday's competition will include high schools and other elite, masters and veteran rowers.