Sweeney made the move to the Mariners ahead of the 2025-26 season.

The 23-year-old defender makes the move to Blundell Park on a free transfer, ending a 16-year association with Leyton Orient. He made a total of 82 First Team appearances for The O’s with 19 of them coming in the club’s League One campaign that saw them narrowly miss out on promotion in the Play-Off Final last season at Wembley.

A Leyton Orient player from the age of seven, Sweeney progressed through every level of their academy, before making his senior debut and signing his first professional deal in the summer of 2019.

During his development, the London-born defender gained valuable first-team experience through loan spells with Bishop’s Stortford, Wealdstone, and Dartford.

He returned to become a regular part of the Orient squad that clinched the League Two title in the 2022–23 season, making 26 appearances.

A powerful and versatile left-sided full-back, Sweeney brings defensive strength and energy down the flank, as well as a wealth of experience for his age.