Wegelius started his career in France, riding for the Vendée U team managed by Jean-René Bernaudeau, thanks to the influence of former pro Graham Jones.

His biggest result was winning the Under-23 section of the Grand Prix des Nations, after which Le Télégramme reported that Wegelius was one of the most promising riders of his generation.

At Mapei he was part of a generation of young cyclists that included Fabian Cancellara, Luca Paolini, Dario Cioni, Rinaldo Nocentini, Filippo Pozzato, Leif Hoste, Bernhard Eisel, Allan Davis, and Michael Rogers.

In 2004, Wegelius notably helped Serhiy Honchar to an unexpected second place, often driving the leading group up the difficult mountain stages.

[9] Having been on the Liquigas-Bianchi team since they reached the top level of cycling, Wegelius was a key domestique in the Giro d'Italia supporting Dario Cioni, Danilo Di Luca, and Stefano Garzelli.

By finishing 45th, he was the best placed British rider in the general classification at 1 hour, 41 minutes and 5 seconds behind yellow jersey winner Alberto Contador.

He received a call-up to participate in the 2009 Tour de France as a replacement for Thomas Dekker, who was ruled out following a positive drug test.