ATHLETICS: With his race run, veteran Australian long-distance runner Craig Mottram says he's excited to see what the next generation of athletes will produce at the Rio Olympics.

The 35-year-old Mottram has been a mainstay in Australian Olympic teams since the Sydney Games in 2000, with his best finish an eighth in the 5000m event in Athens.

His bid to reach an unprecedented fifth Games, by targeting a marathon spot, fell short on Sunday when his finishing time at the London Marathon was outside the qualifying mark.

But Mottram, who insists Sunday's would be both his first and last marathon, was undeterred about missing out on the chance to create Olympic history.

"I've done four (Olympics), so I'm not sad (to have missed out)," Mottram told AAP.

"More importantly, I'm excited for the guys who will get selected in the team.

"There have been one or two who have been before but there will be a new face I'd imagine.

"I'm excited to see who that is and to see how they go."

Michael Shelley is certain to be picked, having run times of 2:11:19 and 2:12:20 in the qualifying period.

Who will join the 32-year-old, who won marathon gold at the 2014 Commonwealth Games in Glasgow, remains to be seen.

Veteran Scott Westcott (2:15:30) and 26-year-old Brad Milosevic (2:16:00) have notched times inside the 2:19:00 qualifying mark, and 29-year-old Liam Adams posted 2:14:58 at the Warsaw Marathon also on Sunday.

"It's time now for our sport in Australia to have some new faces coming through," Mottram added.

"I've done my time and I've enjoyed it, but I'll be watching Rio from Melbourne and I'm OK with that."

AAP