Team Sky's Richie Porte was hit with a two-minute penalty for receiving a wheel from Simon Clarke after a late puncture on stage 10 threatened to detail his Giro d'Italia hopes.
The punishment means the Australian now trails Alberto Contador (Tinkoff Saxo) in the Maglia Rosa by three minutes and nine seconds.
Nicola Boem (Bardiani-CSF) took the stage win in the 200-kilometres route from Civitanova Marche to Forli as Contador enjoyed an uneventful day to retain the overall leader's pink jersey, but Porte's day proved rather more dramatic.
Having started the day 22 seconds off the lead in in third, he suffered a costly puncture 5km from the finish.
Porte's fortunes would have been worse but for the sportsmanship of compatriot Clarke, the Orica-GreenEdge rider giving Porte his wheel to help to minimise time losses.
The mishap initially saw Porte lose 47 seconds to Contador to slip to fourth, but worse was to come on Tuesday evening when it emerged he had contravened a UCI ruling for 'non-regulation assistance to a rider of another team'.
Organisers confirmed a jury of commissaires had studied the incident and given Porte and Clarke two-minute penalties and fines of 200 Swiss Francs.
The penalty sent Porte back to 12th place in the general classification.
Team Sky principal Sir Dave Brailsford said on www.teamsky.com: "It is obviously disappointing that a sporting gesture made in the heat of the moment has resulted in such a strong penalty. No one was trying to gain an unfair advantage.
"This has however just strengthened our resolve and determination to fight for this race. Richie and the whole team are ready to take it on and there is a lot of this Giro left."
Earlier in the day Porte wrote on Twitter: "Not the best of luck for me today but guess it could have been worse. Ready to fight all the way to Milan!
"If that's not Aussie mate ship then what is? Punctured and clarkey gave me his front wheel."
Clarke told cyclingweekly.co.uk: "He punctured and obviously needed a hand. It could have cost him the Giro."
