Walsall’s promotion hopes were severely dented after a comprehensive defeat at Barnsley in the first leg of their League One play-off semi-final.
Jason Demetriou’s 45th-minute own goal put the Tykes ahead before Sam Winnall’s quick-fire second-half brace secured a deserved win.
The Saddlers now have it all to do in Thursday’s return leg.
Head coach Jon Whitney kept faith with the same team that thrashed Port Vale 5-0 at Vale Park last weekend.
With so much at stake, it was perhaps unsurprising that the opening quarter of an hour was a cagey affair with no real goalmouth incident.
Barnsley threatened first on 17 minutes, Lloyd Isgrove with a well-struck 25-yarder which visiting keeper Neil Etheridge smartly tipped over.
Walsall responded with Kieron Morris feeding top scorer Tom Bradshaw who fired straight at home stopper Adam Davies from inside the box.
Wales international Isgrove was looking dangerous for the hosts and on 22 minutes he had the ball in the Saddlers’ net.
Adam Hammill’s wonderfully inviting cross was volleyed home by the Southampton loanee, only for the goal to be disallowed for offside.
The home fans were incensed by the decision – which television replays showed to be incorrect.
Whitney’s Saddlers, who finished the league campaign ten points ahead of the Tykes, then created a few openings themselves.
Anthony Forde’s 20-yard free-kick was palmed away one-handed by Davies, who also held Demetriou’s effort from Romaine Sawyers’ cut back.
Five minutes before half-time, the visitors fashioned a golden chance.
Morris’ raking pass found Milan Lalkovic, who skinned Josh Scowen and cut the ball back for Bradshaw to side-foot wide from ten yards.
And Walsall were left to rue that missed opportunity as Barnsley made the breakthrough on the stroke of half-time.
Winnall’s accurate pull-back found Hammill, whose first-time shot was heading wide until it deflected in off the luckless Demetriou.
HALF-TIME: BARNSLEY 1-0 WALSALL
The Tykes, with one defeat in their previous ten, wasted an excellent chance to double their lead shortly after the resumption.
As Barnsley broke four-on-one, Isgrove chose to go it alone instead of pass to a teammate, with Etheridge parrying his powerful effort.
Walsall then went close at the other end, as Lalkovic jinked past Scowen before being denied by the legs of Davies.
But the Saddlers’ hopes of a comeback were dashed on 54 minutes.
Winnall was afforded too much time and space to unleash a 20-yard strike which took a wicked deflection off Jim O’Connor and flew over Etheridge.
And - in the blink of an eye - Barnsley made it 3-0.
The prolific Winnall was again Walsall’s tormentor-in-chief as he collected possession from deep and drove purposefully at their defence.
He held off the challenge of Forde and glided effortlessly past Paul Downing before calmly finishing left-footed across Etheridge.
With less than an hour played, Walsall’s Wembley dreams were already hanging by a thread.
Whitney turned to his bench and brought on Sam Mantom and Jordy Hiwula in place of Morris and Bradshaw.
And the Saddlers began to show signs of promise, with Forde delivering a low driven cross from the right which just eluded the stretching Lalkovic.
Walsall threatened again on 75 minutes, when Sawyers superbly slipped in Mantom but, leaning back, the midfielder blazed horribly over.
That proved the visitors’ final chance as Barnsley comfortably saw out the closing stages to take control of the tie.
FULL-TIME: BARNSLEY 3-0 WALSALL
Etheridge, Demetriou, O’Connor, Downing, Henry, Chambers, Morris (Mantom 60’), Lalkovic (Cook 84’), Forde, Sawyers, Bradshaw (Hiwula 71’).
Subs not used: MacGillivray, Taylor, Preston, Osbourne.
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