Though Knapp was the underdog in a few senses - ranked No.48 to Vinci's No.42, and seeded No.6 to Vinci's No.4 - she went into the match with confidence from winning three of the pair's five previous meetings, including their only meeting this year, a come-from-behind win on the clay of Marrakech.
Vinci certainly had her chances this time - she led 5-2 in the first set, even holding two set points at 5-3, and after letting that first set go, she won the second set and held at love for 1-0 in the third.
But from there it was all Knapp, who won six games in a row to close it out, 7-6(5), 4-6, 6-1.
Knapp now has two WTA titles to her name, having won in Tashkent, Uzbekistan last fall.
"I'm really, really happy to win the title," Knapp said. "It's never easy against Roberta, and as you saw it was a close match. But it's great to get the win and gain some good confidence for the French Open."
In spite of the loss, it was a very positive week for Vinci - she's been starting to show the fantastic and unique brand of tennis that took her as high as No.11 on the WTA Rankings a few years ago.
"I tried my hardest today, but I'm pleased to have reached the final," she said. "Karin played very well today. It was a tough match. We've known each other for a long time, so it's tough to play her.
"I'll just relax the rest of the day, and try my best in Paris next week."
Knapp against Vinci was the first all-Italian final on the WTA since July 2013, when Vinci beat Sara Errani in the final of another International-level clay court tournament over in Palermo, Italy.
The doubles final was played earlier in the day and saw No.2 seeds Chan Hao-Ching and Anabel Medina Garrigues fight off a set point down 5-3 in the second set and claw back from 4-1 down in the ensuing tie-break to close out No.4 seeds Lara Arruabarrena and Raluca Olaru in straights, 6-4, 7-6(5).
Chan took home her sixth WTA doubles title while Medina Garrigues captured her milestone 25th.
? WTA (@WTA) May 23, 2015