Martin Lel's ambitions of becoming the first man to win four Flora London Marathon titles could rest upon a scan for a hip problem.
The Kenyan had enjoyed a trouble-free build-up in his quest to better the three victories achieved by Mexico's Dionicio Ceron until he felt a pain in his back last week.
The 30-year-old defending champion, who posted a course record of two hours five minutes 15 seconds a year ago, insists he will be ready for Sunday's race but will have the MRI scan as a precaution to discover the extent of the problem. If the test diagnoses a more serious injury Lel will not rush his decision about pulling out.
He explained: "For now I'm still confident of running, in my mind I'm still preparing to run on Sunday."
Lel's coach, Gabriele Rosa, explained: "If necessary we will wait until just before the race starts before making the decision." Sammy Wanjiru, Jaoaud Gharib and Tsegaye Kebede, the first three finishers in last August's Olympic marathon are included in the elite line-up.