The versatile Leigh has signed for another step 3 club after being released by Bognor Regis at the start of this month.
He had to wait for his Boro debut, though, due to the fact he was serving a suspension after being dismissed in his last Rocks outing at Folkestone on February 26.
The former Horndean and Baffins Milton Rovers man lasted 65 minutes in a dramatic 2-1 victory at lowly Merthyr Town before going off with a tight calf.
Leigh played in a role just off central striker Matt Paterson in a new-look Boro formation where boss Shaun Gale deployed three centre halves in Luke Hallett, Matt Briggs and Ryan Woodford.
‘Ashton rang me a few week ago to say he was leaving Bognor and would I be interested,’ explained Gale. ‘Of course I was interested - Ashton’s an extra body, we haven’t got bundles of players.
‘He’s experienced at this level, even though he’s a young lad, he’s got a good left foot and he can play in numerous positions - left back, centre half, midfield.’
Leigh is a squad replacement for Mason Walsh, who has returned to America.
Briggs’ late winner - heading in after Luke Hallett had nodded a recycled corner back across the penalty area - provided Gosport with realistically the only result they needed to keep alive play-off hopes.
They are now just three points behind Chesham, who occupy the last play-off place in fifth place, with six matches remaining. And Gosport still have to visit Chesham.
Of greater concern is the fact that both Weston-super-Mare and Yate remain above eighth-placed Boro with one and three games in hand respectively.
‘It was a professional, hard-working performance,’ Gale stated of the victory in south Wales against the second-bottom Martyrs.
‘I told the players beforehand, it wasn’t a case of how you win, it was a case of we must win - but the performance was good from us. I know we scored late but it would have been a travesty if we hadn’t won. They only had one shot and scored from it.’
Boro travelled light in numbers with top scorer Dan Wooden and Dulwich loanee AJ Harris-Sealy injured and Ryan Pennery and Matt Casey ill.
They went ahead on 39 minutes through a superb goal from Paterson, volleying in from the edge of the penalty area.
Merthyr levelled just after the hour mark through Curtis Jemmett-Hutson before Briggs nodded in his first league goal since early September.
The game was held up for around 10 minutes in the second half following a collision between Boro pair Rory Williams and Harvey Rew.
Williams was forced off with a swollen jaw while Rew carried on, complete with a bandaged head.
Next up for Gosport is a home clash with Taunton Town, who have won 13 of their last 15 league fixtures and who would go top if they won their game in hand.