Gambhir's own coaching style also faced heavy criticism as India's batters folded for 201 or less in every innings in the two-match series, handing world test champions South Africa their first series win in the format on Indian soil since 2000.
It was India's heaviest defeat by runs in the format, eclipsing a 342-run loss to Australia in 2004.
"Four or five batters in this top eight have played literally less than 15 test matches," Gambhir told reporters.
“And they will grow, they are learning on the job. They’re learning on the field. Test cricket is never easy when you are playing against a top-quality side. See, you’ve got to give them time as well... this is exactly what transition is."
Gambhir, who took over last year, was asked if he was the right person to be coaching India's test team.
“It is upon (the Indian cricket board) to decide... Indian cricket is important, I’m not important," he answered.
"And people keep forgetting about it, I’m the same guy who got results for the team in England. With a very young team. And I’m the same guy who won the Champions Trophy and the Asia Cup as well."
Under Gambhir, India drew a test series with England in June-July, after winning the 50-over Champions Trophy in March. They also won the 20-over Asia Cup in September.
"If we want test cricket to flourish in India, we need an overall effort. We can’t put things under the carpet. If you get runs in the white-ball format, you forget what you’ve done in red-ball cricket. That shouldn’t happen," Gambhir said.
India play South Africa in three One-Day Internationals from November 30, followed by five Twenty20 matches starting December 9th as they prepare for next year's T20 World Cup on home soil.