"At the present moment, Yuvraj is the first choice considering the number of games he has won for us," Ganguly said after arriving in Bangalore on Sunday to attend a training camp along with his teammates.
Left-handed Yuvraj, 22, has played just four Tests in the middle order, but Ganguly said the batsman had the ability to succeed in his new role.
"Virender Sehwag also never used to open before, but has done amazingly well. Yuvraj has got the ability to open the innings and a player of his stature should not be kept out of the team," he said.
Sehwag, who started his career as a middle-order batsman, made history when he smashed 309 as an opener in the first Test against Pakistan at Multan in March to become the only Indian to score a triple-century in Test cricket.
Ganguly said Yuvraj would also get used to the opener's slot.
India tried two different pairs on their recent historic tour of Pakistan, with Sehwag opening with Aakash Chopra in the first two Tests and with Parthiv Patel in the third and final match.
The Indian captain's remarks meant that Yuvraj was set to replace Chopra as an opener for the upcoming home Test series against Australia and South Africa.
"There is a place open for Yuvraj as an opener and if he does not perform well, we will think of somebody else," said Ganguly.
Yuvraj shot to fame with an explosive 84 against Australia in the ICC Trophy Limited Overs tournament in Kenya in 2000. He has so far scored 2,212 runs in 94 One-dayers.