Chris Froome offers Grand Tour advice to departing Richie Porte

After helping Team Sky win three editions of the Tour de France, Richie Porte is leaving the team to pursue his own Grand Tour ambitions. Froome said he will miss his friend and offered his advice for grand tours: "Be more consistent."

Froome will win the Tour de France on Sunday when it ends in Paris barring a disaster. On Saturday he defended his yellow jersey on the last testing stage to Alpe d'Huez with the help of team-mate Porte.

A confirmation has yet to come, but Porte is reportedly likely to ride in BMC Racing's red and black colours in 2016. He should lead the team in the week-long stage races – this year he won three including Paris-Nice – and in grand tours.

"Where does he need to improve?" said Froome. "Probably in consistency. To be able to look at a three week race [you need] to roll with the bad days as well as the good days."

Porte served Sky well as a super domestique: helping Wiggins to the 2012 Tour title and Froome to the 2013 and, if all goes well, the 2015 title.

However, he has been unable to follow through when given leadership in a three-week race. Last year he fell sick before his chance to race and lead the team in the Giro d'Italia. This year, he crashed and had to abandon the Italian tour in its second week.

In the Tour de France last year, he was given his chance to lead after Froome abandoned due a crash. Still feeling the side effects of pneumonia, though, he suffered and fell out of contention on the stage to Chamrousse.

Critics say that he is prone to suffer a bad day but Froome recognised the Tasmanian's raw talent.

"I hope [him leaving] won't affect our friendship I'd like to think that will remain the same," Froome said.

"Richie is an incredibly talented climber, probably one of the best riders in the peloton. There are often times he drops me in training and racing. There's no doubt, he has the ability. I have no doubt that he has the ability to ride the GC in a grand tour."

Porte trained alongside Froome and helped ready him for the Tour. Besides riding together from their homes in Monaco, the two reconnoitred several important stages. One important day was in the Pyrenees, when Froome said to his training partners and sports director Nicolas Portal where he would attack his rivals.

"I chose La Pierre-Saint-Martin to make my move, even weeks before the Tour,” Froome explained.

"I thought, those gradients at 10% and knowing that it flattened out in the final four kilometres, I wanted to attack one kilometre before that, and go into time trial mode and hold them off. I thought, if anyone is trying to catch up on a less steep finish, it will favour me.

"I had that scenario in my head three weeks before the Tour started.

“As far as the Alps, the gradients are not quite as savage as they are in the Pyrenees. I hoped to have an advantage, just to defend it.

“That was my plan and my strategy. Nairo Quintana said that he wanted to attack in the Alps. He did. My tactic was to hang on. I did."

Froome gained 1-04 on La Pierre-Saint-Martin in southwest France. Over the next week and a half, he "held on" as Quintana made up ground.

Though he lost 1-26 on Saturday, he still has a 1-12 buffer that will allow him to take his second Tour title today in Paris.

Watch highlights from stage 20 of the Tour de France