Keith Paddock’s men led early on when hooker Toby Welsby spotted a gap in the Siddal rearguard and exploited it via a superb dummy before racing 20 metres to touch down.
Marcus Paddock converted and the home side led 6-0.
Siddal, who fielded several of their first team squad for the clash, hit straight back with two converted tries to make it 12-6, but the Pirates were back level heading into the break.
Nathan Hakings touched down to shorten the deficit and Paddock calmly converted again for 12-12 at the interval.
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It was the Pirates who started the second half on the front foot much as they did in the first and they soon regained the lead when Jamie Cornish showed his electrifying pace to leave the Siddal defence in his shadows and charge almost 70 metres to touch down.
Josh McNeil converted successfully and the Pirates were in charge.
Their lead was furthered shortly after when Siddal were penalised in front of their posts and McNeil slotted home with the boot to make it 20-12 and seemingly hand the home side the win.
Siddal had other ideas though and threw on super-sub Josh McDonald, who turned the game on its head.
McDonald’s speed and agility proved too much for the weary Pirates backline to handle and he ran in 10 unanswered points to help Siddal to the victory.
Coach Paddock wasn’t too disappointed with his side’s efforts on the day, he said: “It was a game we really wanted to win as we lost at their spot by four points and we played probably the worst game of our season.
“So we were confident that Saturday was going to be our day. It was one of the best games of the season so far.
“They were a great opposition, there was plenty of banter on field which always makes it interesting and on the positive side, they admitted to playing most of their A team so we’re taking some comfort from that.”
“We have two games left this season and they will be our toughest of all as we play Lock Lane and Cutsyke away.”