The performance of the Indian openers since Gavaskar's retirement and their partnerships show that India's fortunes in test cricket are quite well correlated with them. Their middle order has always been strong, but vulnerable against the new ball if early wickets fall. Sidhu did quite well in the 90s, but never found a steady partner. India tried part-time openers with him - Prabhakar and Mongia in particular, but they didn't have as much success especially outside the subcontinent.
They managed to challenge Australia at the height of their dominance through the early 2000s and claw their way to No 1 after Australia's decline. The partnerships table clearly shows Sehwag (in partnership with Banger, Jaffar, Chopra, Gambhir and Vijay) dominating that list. The interesting one is the success of Karthik and Jaffar with some big partnerships in 2007 at the height of India's success.
With Sehwag's international career probably over, the success of the Indian team will hang on the performance of their new openers. Vijay has had success in partnership with Sehwag, but Gambhir's loss of form hurts India just when his experience would have helped with the transition. Shikhar Dhawan made the most of his one appearance against Australia at home, but they'll both be sorely tested in South Africa later this year. They can take solace in the fact that the last batsman to have success early there, turned out to be India's best opener since Gavaskar.