Sky's last-minute decision to take Porte out of the early-season French stage race and make him team leader at Tirreno-Adriatico has angered race organisers ASO, who own the Tour de France.

It also means Porte will go up against fellow Australian star Cadel Evans in the Italian race.

Porte is the only Australian to have won Paris-Nice.

Tour de France and Parisrace director Christian Prudhomme was unimpressed with Porte's late withdrawal.

The Tasmanian had star billing at Paris-Nice, where he would have competed against top Italian Vincenzo Nibali and Portugal's reigning world road champion Rui Costa.

"We find it cavalier to have the reigning champion pull out just before the start," Prudhomme said.

"We were told that to win points for the world rankings, the Tirreno was more favourable [to Porte] due to its technical characteristics and the presence of an [individual] time-trial."

Froome, the reigning Tour de France champion, announced on Twitter he had slight inflammation in his back.

"So I will be putting my feet up for a few days on doctors' orders," he said.

"It's disappointing to miss out on a week of solid racing, but rather safe than sorry at this point of the season."

The sudden change does not change Porte's program too dramatically, given Paris-Nice is from March 9-16 and Tirreno-Adriatico runs from the 12th to the 18th.

Porte's main goal this year is the May Giro d'Italia (Tour of Italy), where he will ride against Evans among other overall contenders.

He then plans to help Froome in the British rider's Tour de France title defence.

Tirreno-Adriatico offers a more suitable course for Porte's abilities than Paris-Nice this year, with two summit finishes and an individual and team time-trial.

Porte and Evans started their seasons with strong form in January at the Australian road championships.

Evans was runner-up behind Simon Gerrans and Porte finished third.

The pair continued to impress a few days later at Adelaide's Tour Down Under.

Evans rode brilliantly on the tough Corkscrew climb to win stage three and was runner-up overall, one second behind Gerrans.

Porte also posted a win at the key Willunga stage and finished fourth overall at 10 seconds.