Gate opened the Hallmark Security League season with a premier division defeat in Cheshire, where all the goals came in the second half.
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They handed a debut to Chris Morris in defence and welcomed back Jake Higham and Josh Westwood to the club. New signings Josh Pollard, Luke Noble and Ryan Dodd were all on the bench.
Gate were on the back foot from the start against one of the favourites for promotion and had a let-off after four minutes, when striker Simon Thelwell shot tamely wide from a free-kick to the back post.
Forbes had Runcorn’s next shooting chance from Craig Cairns’ pass, while at the other end Mututu Chilufya struck wide.
Striker Cairns dispossessed Gate but could not find his target with the shot, though he went closer when a defence-splitting pass left him one-on-one with Josh Woods, the Gate keeper standing tall to turn the shot against the crossbar.
Gate’s best chance of the first half came five minutes before the break, when James Boyd’s initial shot was saved by Adam Reid and his follow-up effort was cleared off the line by defender Marcus James.
Woods again denied Cairns just before the break, tipping his header over following a fine cross.
The home side made the breakthrough 10 minutes into the second half, when Joe Holt was given too much time to pick his spot from 20 yards.
Noble made an instant impact after coming on for his Gate debut in the 66th minute. He was sent through one-on-one with keeper Reid, who did well to deny to striker.
Runcorn then turned on the style and doubled their lead four minutes later.
The influential Cairns was sent through by Paul McManus and made no mistake in slotting the ball past Woods.
Noble’s curled effort was easily dealt with by Reid but the striker got the consolation goal Gate deserved on 82 minutes, rounding the keeper to tap into an empty net.
Both keepers made further good saves as Town’s Holt and Gate’s Noble were again denied.
Game will look to get off the mark for the season at home to Burscough on Tuesday (7.45pm).
Gate: Woods, Mullen, Morris, Westwood, Higham, Staunton-Turner, Boyd, Ing, Riley, Egidi, Chilufya. Subs: Pennington, Pollard, Dodd, Noble, Charnley.
AFC Blackpool began their first division north campaign with a 2-1 home defeat by Steeton.
Ben Clarkson gave an 11th-minute lead to the Yorkshire club and Jack Richmond doubled their advantage on 34 minutes only for Joe Robinson to pull one back a minute later.
AFC are in action at the Mechanics Ground again on Tuesday, when Cleator Moor Celtic are the visitors (7.45pm).