Trial and error: Who has what it takes to make the U.S. Olympic marathon team?

2 days until #LA2016! Prediction time: who do you have winning Saturday and who makes your #TeamUSA for #rio2016? #marathon #?? #?

A photo posted by USATF (@usatf) on Feb 11, 2016 at 12:36pm PST

The biggest race in four years for U.S. athletes is taking place this Saturday in Los Angeles as the Olympic marathon trials takes centre stage ahead of Rio 2016.

The top three men and women in Saturday’s race will earn a spot on the U.S. Olympic team heading to Rio for the Games which begin in August.

There is no equivalent to the U.S. marathon trials in Canada largely because the Canadian Olympic standard is 2:12:50 (men) and 2:29:50 (women) is much tougher than the U.S./Olympic standard (2:19 and 2:45, respectively).

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#LA2016 bibs are indahouse! pic.twitter.com/S23PMn4P8M

— Sam Grotewold (@nyrr_pro) February 9, 2016

Here are four athletes to watch out for in both the men’s and women’s races.

Men’s Race 1:06 p.m. EST

Who to watch out for in the men’s race

Meb Keflezighi — The 2004 Olympic silver medallist in the marathon would be the oldest U.S. Olympic runner in history if he’s able to qualify for Rio.

Dathan Ritzenhein — Nicknamed “Ritz,” the 33-year-old has the fastest marathon personal best in the men’s field (2:07:47) from 2012. Injuries have plagued Ritzenhein in the past but he has made the Olympic team each of the past three occasions (2004, 2008, 2012).

Galen Rupp — Rupp is arguably the best distance runner in the United States having won an Olympic silver medal in the 10,000m at the 2012 Olympics in London. He holds the 10,000m record and has run 1:00:30 in the half-marathon. He’s never run a marathon and will be making his debut in L.A.

Sam Chelanga — Chelanga has all the credentials to make the U.S. team but again, as a debutant at the 42.2K distance, relying on past performance to predict the possible outcome is risky. Only Rupp has faster PB’s over.

Notables Ryan Hall and Ryan Vail have withdrawn from the race. Also keep an eye out for Luke Puskedra, a 6’4 big man.

Luke Puskedra: "I have a tendency to overdue everything." Turned home thermostat up to 80 for indoor workouts. pic.twitter.com/75T46msZRf

— Mario Fraioli (@mariofraioli) February 11, 2016

RELATED: Chris Zablocki: The most fascinating man running the 2016 U.S. Olympic Trials.

Women’s Race 1:22 p.m. EST

Who to watch out for in the women’s race

Shalane Flanagan — With a 2:21:14 marathon to her name and having set American records in multiple events, including the 10,000m record which she still has, Flanagan is one of the safer bets to make the team.

Kara Goucher — Though she has one of the stronger lifetime bests (2:24:52) of the field, the 37-year-old will be in tough to make her third Olympic team. She won bronze in the 10,000m at the 2007 World Championships.

Desi Linden — Having run 2:22:38 for the 42.2K distance, Linden should make the Olympic team if she can replicate that type of performance. She dropped out of the Olympic marathon in 2012 due to a femoral stress fracture. She won a Pan Am Games silver in Toronto in the 10,000m.

Amy Cragg — Having placed in the top-12 in the Olympics, Cragg, 32, has trained with Flanagan for much of the fall and enters Saturday as one of the contenders to make the top-three.

American record holder Deena Kastor withdrew from competition on Thursday.

Temperatures will be hovering around 30 C on Saturday which is expected to have a significant effect on the athletes. Don’t be surprised if lesser known runners (Elkanah Kibet on the men’s side and Becky Wade in the women’s race, for example) makes a push for an Olympic spot.