London Marathon winner Wilson Kipsang has urged Britain's Mo Farah to concentrate on either the track or the road in the future, not both.
Farah, who struggled to keep pace with the leaders in his debut Marathon race, has yet to make it clear whether he will concentrate solely on the road by the time the Olympics in 2016 are here.
The Kenyan, however, believes that performing well in both would be impossible, adding there would be no chance of winning on track and road in Rio.
"No, no, no, no, it's not possible," he said. "The marathon and 5k and 10k, you can not do it. You will not even reach halfway.
"The rhythm, how you have to run, is totally different between track and road racing. You'll be disturbing the body so much."
Farah, however, was quick to state he would be back to run another marathon: "That's who I am," he said. And it doesn't look like he is going to give up the track either.
He is competing at the Glasgow Diamond League meeting in July, and has track titles to defend at the World Championships next year, before the Olympic year in 2016.
Kipsang, though, who beat the Brit by nearly four minutes on his way to a course record in London, is adamant training for both disciplines will hinder Farah.
"You automatically lose because the training for a marathon and the training for a 10k on the track is totally different."
If Farah were to compete in both, he would be bidding to become the first person to win both the 10,000m and the marathon at an Olympic Games since legendary Czech runner Emil Zatopek completed the feat at the 1952 Helsinki Olympics.
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