"It's a prime position to be in to lead the team," Porte told Sydney Morning Herald. "I'm definitely going to take this chance to prove that I can be up there on the general classification."
"He's in great shape," team boss, David Brailsford said at the stage finish on Wednesday. "He's had a slower start to the season than normal, he's fresh. His form has come in at the right time. He's climbing well. That's the reason why we decided to take him as our second rider."
Froome crashed twice and abandoned yesterday ahead of the cobbled sectors of stage five. He left the 29-year-old Australian to take the reins of the team as it races east to the mountains. Despite falling early on Wednesday, he bounced back in the cobbled stage and finished 1-52 minutes back to move to eighth overall at 1-54 behind race leader Vincenzo Nibali (Astana).
Porte was Froome's right-hand man last year in the Tour de France and helped him to win the race. He was even considered as a back up plan until he lost time in the stage nine in Bagnères de Bigorre. He went on to place 19th.
Sky took on Porte in 2012 after he placed seventh in the 2010 Giro d'Italia as a first-year professional with Saxo Bank. In 2012, he helped Wiggins and Froome in the Tour and in 2013, he blossomed. Porte won the Paris-Nice stage race and placed second in the Criterium International, País Vasco and the Criterium du Dauphine.
Porte was due to lead Sky's Giro d'Italia team this spring but had to cancelled his plans after stomach problems ruined his run up. He bounced back well in the Dauphiné and received the green light to ride lieutenant to Froome in the Tour de France.
"One man's loss is another man's opportunity isn't it?" Brailsford continued. "This is a great opportunity for Richie and we really believe in him. He is coming into some great form. He just has to try and enjoy [the chance to lead the team] and take the opportunity."
Porte added: "The change in role and how it has come is a lesson in how quick circumstances can change for you not just in a bike race, but in your career; and how opportunity can come to you without warning."
Team Sky boss speaks after defending champion Chris Froome crashes out of stage five and abandons the race
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