Mark Cavendish has withdrawn from next week's London Six Day event after only recently returning to training following a six-week lay-off with Epstein-Barr virus.
The 33-year-old was in August diagnosed with Epstein-Barr virus, commonly known as glandular fever, for a second time in 18 months, bringing a premature halt to his road season.
The 30-time Tour de France stage winner, a three-time Madison world champion on the track, returned to training earlier this week, but will not compete in the event, which is as much about entertainment as sport.
Cavendish wrote on Twitter: "Disappointed to say, after just 4 days training since recovering from my illness, I won't be riding @sixdaycycling London. Gutted. I'll be there supporting though. Always a great party."
Cavendish's future remains uncertain, as his contract with Team Dimension Data expires at the end of the calendar year and there is no news on who he will be riding for in 2019.
Cavendish has finished as London Six Day runner-up in the last two years - in 2016 with Sir Bradley Wiggins and in 2017 with Pete Kennaugh.
The Six Day event takes place at Lee Valley VeloPark, formerly known as the Olympic Velodrome, from October 23 to October 28.