Substitute Jisung Eom struck a late winner as Swansea City ground out victory over Derby County at the Swansea.com Stadium.
The South Korea international snuck in at the far post to meet an inswinging cross with 11 minutes to play, settling a contest that was often a tense, cagey affair.
There was no doubting the effort levels on display in a game between two sides who knew a win would move them considerably closer to securing Championship status for next term, but a lack of patience and composure in the final third ensured there was little in the way of clear-cut chances.
But the hosts made sure they claimed an 11th clean sheet of the season, and Eom made no mistake when given the chance to net his second Swansea goal.
The Swans had been unchanged from the draw at Leeds, while the visitors brought Kane Wilson, Sondre Langas and Kayden Jackson into their team following the midweek win over Preston that had hauled them out of the bottom three.
Sheehan had warned his team to expect a dogfight against a physical and in-form Rams team, and the visitors started the game by putting plenty of balls into the box for the Swans to deal with.
The opening 17 minutes passed with barely a glimmer of genuine goalmouth action, although Craig Forsyth would have had a chance to turn in at the far post for the visitors had he better anticipated a flick-on from a free-kick.
Forsyth ought to have done better when a pull-back found him ahead of his man near the six-yard box, but his effort was blocked.
Jackson’s pace then threatened to get him in behind Ben Cabango, but the Swansea captain recovered and Harry Darling cut out the final in-field pass.
Wilson hit the side-netting from an acute angle following a Matt Clarke flick-on but the game remained goalless after an eminently forgettable opening half.
Swansea started the second half the brighter of the two teams, with Ronald, Josh Key and Josh Tymon all delivering into the box but being unable to find white shirts amidst the massed ranks of the Derby rearguard.
The hosts began to enjoy periods of sustained pressure, and they forced a series of set-plays around the hour mark but a strong claim from Jacob Zetterstrom in the Derby goal brought that sequence to an end.
Sheehan turned to his bench, introducing Jisung Eom and Žan Vipotnik for Hannes Delcroix, and the Korean made an important intervention within seconds of coming on as he cleared with Wilson attempting to reach a loose ball that had come through to the far post.
Wilson then failed to pick out Jackson at the end of a Derby counter-attack, while Lewis O’Brien sent a strike from distance high over the bar as the final 20 minutes beckoned.
Marcus Harness looked to profit as the ball bounced around the Swansea goalmouth, but referee Andy Davies was quick to blow for a foul as the Derby forward manhandled Darling in the box.
Vigouroux became the first keeper to make a save of note when he saved Harrison Armstrong’s low strike.
But it was Swansea who landed the decisive blow when Key swung in a cross and Wilson was unable to prevent Eom arriving to convert from close range.
And Joe Allen then made a vital late contribution for the second time in the space of three days as his tremendous covering tackle denied Jackson the chance to strike when through on goal.
Swansea City: Lawrence Vigouroux; Josh Key, Ben Cabango (captain), Harry Darling, Hannes Delcroix (Jisung Eom 63), Josh Tymon; Jay Fulton (Joe Allen 77), Lewis O’Brien, Gonçalo Franco (Žan Vipotnik 63); Ronald (Cyrus Christie 90), Liam Cullen.
Unused Substitutes: Jon McLaughlin, Florian Bianchini, Kyle Naughton, Ollie Cooper, Sam Parker.
Derby County: Jacob Zetterstrom, Kane Wilson, Craig Forsyth, Sondre Langas (Kenzo Goudmijn 83), Nat Phillips, Liam Thompson (Tom Barkhuizen 83), Marcus Harness, Kayden Jackson (Lennon Wheeldon 90), Matt Clarke, Harrison Armstrong, Ebou Adams (captain) (Nathaniel Mendez-Laing 83).
Unused Substitutes: Josh Vickers, Jake Rooney, Jeff Hendrick, Erik Pieters, Kai Robinson.
Referee: Andy Davies
Attendance: 16,501
