Barnsley suffered a first defeat of the season on Tuesday night.
Peterborough United took home all three points after a second half fightback in Sky Bet League One action at Oakwell.
Our number one, Liam Roberts had to be sharp inside the opening few minutes, with a fine double stop to thwart Mason-Clark and Randall.
Soon after that, the Reds began to show their own attacking intent and Max Watters was just inches away from connecting with a low cross.
Our first shot on target came through Jon Russell. The midfielder running onto the ball at the edge of the box but his powerful effort was well saved by Bilokapic in the Posh goal.
There were further chances for both Nicky Cadden and Devante Cole, but the luck wasn't with the Reds, at all, with the ball somehow staying out of the visitors' goal.
It had been an end-to-end first half, but goalless.
HALF TIME: Barnsley 0-0 Peterborough
The Reds forged ahead on 53 minutes when Barry Cotter's fizzing drive came off the 'keeper and flew into the bottom corner.
But we couldn't build on that lead. Instead, we had Roberts to thank for a number of outstanding saves, one in particular with one hand to deny Clarke-Harris. But an equaliser looked on the cards considering the pressure.
It was Kyprianou who found the leveller. A great first-time strike from the edge of the box after a lovely low cross from the right flank.
Within a minute, Posh went in front. Clarke-Harris, who was judged to be marginally onside was able to tap home on the goalline. And two became three soon after when the Reds failed to deal with a ball inside the box, and Poku was able to fire into the top corner.
A disappointing evening at Oakwell and a first defeat of the season.
FULL TIME: Barnsley 1-3 Peterborough
Roberts, Cotter, Williams, Łopata, Kitching, Cadden, Kane, Russell (Phillips), Styles (de Gevigney), Cole (Shaw), Watters (Dallas).
Unused: Killip, Lofthouse, Chapman.
