India need 'special effort' to beat England in semi-final: Gambhir
Samson timed his innings to perfection as the defending champions chased down 196 in the winner-takes-all Super Eights clash to win by five wickets in front of 67,000 fans at Eden Gardens.
Samson played only one group stage game, against Namibia, scoring 22, as India opted mainly for the double left-hand opening combination of Ishan Kishan and Abhishek Sharma.
He was brought back into the side in the previous Super Eights match against Zimbabwe to provide a right-handed option at the top of the order.
Samson scored 24 and Gambhir saw enough to keep faith with him against the West Indies.
The coach was rewarded with a sparkling knock containing 12 fours and four sixes as he made an unbeaten 97 off 50 balls in India's 199-5.
"We all know how good a player Sanju is," Gambhir told a post-match news conference.
"It was all about backing him and when the team needed him the most.
"Obviously today was the day when he probably showed his full potential.
"I have always said that he is a world-class player. He is a great talent and hopefully he can kick on from now and we can see a lot more innings like this."
India now move on to Mumbai's Wankhede stadium and a semi-final on Thursday against England.
Harry Brook's side won all their Super Eight matches and have been ominously improving as the tournament gets to the sharp end.
"Look, they're a world-class team, they're a quality team, they've got a lot of quality players as well," Gambhir said when asked by AFP for his thoughts on the semi-final match-up.
The Wankhede stadium will present very different conditions to Kolkata, and that will mean new challenges, said Gambhir.
"We all know that playing at the Wankhede is a tough game, but it's another opportunity to do something special for the team and for the country.
"Hopefully we play our best game, that is going to be very important and we can keep ticking all the boxes."
He noted that England were dangerous and growing in confidence so nothing less than 100 percent would be good enough if India are to progress to next Sunday's final in Ahmedabad.
"That is going to be important," Gambhir said.
"Because we will need a special effort to beat a quality side like England."