No one has more wins than Kudermetova in doubles this year but she came into Paris having lost in the singles first round in Madrid and Rome, after reaching the final in Istanbul.
Kudermetova was having plenty of success at the net but the problem for both women was holding serve.
As the second set wore on, service holds were at a premium but Kasatkina had the chance to serve it out when she led 5-4 only to show obvious nerves as she failed to finish off the match.
Kudermetova held for 6-5 and then took a medical timeout for what looked like a left foot problem. Kasatkina tried to keep herself fresh during the break and when it came to her turn to serve, she held well to force a tiebreak.
The players switched sides with Kasatkina leading 5-1 and she extended it to 6-1, giving herself five match points.
Things got tense again and Kudermetova hit back to 6-5. But at the fifth time of asking, a brilliant drop shot from Kasatkina gave her a dramatic, emotional victory.