The Morton keeper, who was making his first start since 27 December due to a thigh injury, produced a superb reflex stop to thwart former team-mate Andy Barrowman.
With his side leading 1-0 at the time, Gaston’s contribution proved pivotal as the Ton went on to claim the three points, as well as a rare shutout.
Duffy said: “Gats made an outstanding save from Andy Barrowman’s header and I said that to him in the dressing room afterwards.
“He was going one way and stretched the other way to save — and these are the things that hadn’t gone our way recently; any wee mistake we’ve made would have usually been punished.
“We got away with a header in the first half and Gats has made that great save; those were the two opportunities Dunfermline had but I felt we defended really well the rest of the time.
“As a coach I’m delighted because it’s the first clean sheet we’ve had since last year. That gives you a platform to go and compete in the game.”
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