Canada's Stafford sisters both advance to women's 1,500m semifinals

Toronto sisters Gabriela Debues-Stafford and Lucia Stafford are headed to the women's 1,500-metre semifinal together after impressive performances in their respective heats.

Gabriela, the Canadian record-holder in the distance at three minutes 56.12 seconds, won the first heat of the day with a time of 4:03.70.

But the 25-year-old, in her second Olympics, was outdone by younger sister Lucia, 22, who ran a personal best 4:03.52 to finish seventh in the fastest and final heat.

The top six in each of the three heats, plus the next six fastest, book their spots in Wednesday's semifinals. The final goes on Friday.

WATCH | Debues-Stafford eyeing Tokyo podium:

Despite Monday's results, Debues-Stafford remains the better bet of the two to reach the podium amid the stacked middle-distance field.

"I have my eyes set on something big in the finals, so I'm happy that I got the first round done and I felt really good doing it," Debues-Stafford said.

She added that the heats were more competitive than she expected.

"I didn't know what the time was and I thought, 'Oh, this is feeling like a little bit of effort.' I wasn't expecting it to be that fast. I felt like 4.03 and I felt really good, and to do it from the front and to control it the way I did. I'm very pleased with that."

Hassan makes incredible recovery

The Stafford sisters avoided the drama of the second heat, when podium favourite and top-ranked Sifan Hassan of the Netherlands got tangled with a competitor and tumbled to the deck. Hassan was beginning her unprecedented quest for a 1,500, 5000 and 10,000 triple.

The fall dropped Hassan to 11th after 1,200 metres, but she quickly recovered, surging past the front of the pack in the final 300 metres to win her heat at 4:04.17.

WATCH | Hassan tripped, recovers to win heat:

Hassan has qualified to run in the 5,000 final later Monday at the Olympic Stadium, where she's expected to battle with two-time world champion Hellen Obiri of Kenya for gold.

Her grueling schedule means she will have to run six races in eight days in the Tokyo heat and humidity, including the two races on Monday and the 1,500 and 10,000 finals on back-to-back days on Friday and Saturday.

Canada's Natalia Hawthorn, who was involved in the mixup with Hassan, ran a 4:08.04 and failed to advance.

Reigning world champion Faith Kipyegon of Kenya won her heat at 4:01.40, the best time of the day.