Not only was the defender on the winning side, he netted the only goal of the game with a delightful curling effort - a moment his sister insists she will never forget.
"It sounds daft but it hasn't really settled in," she told mcfc.co.uk. "I messaged my brother this morning to make sure he's okay because he was actually taken off injured - but he's fine.
"It was a really lovely day and when he put the ball in the net, it was an incredible moment. I wish I could watch a video of my family jumping up and down and crying.
"It was even more amazing because they actually had a disappointing season and were relegated, so to sign off on a high was great for the fans and I still can't believe he scored the winner!
GOALLL SHAYMMENN!! Scott McManus you beautiful man! @scottmc6 Lovely strike beyond keeper at Wembley. FCHT 1 - 0 Grimsby! #FATrophy— FC Halifax Town (@FCHalifaxTown) May 22, 2016
"I'd been given the day off by
Talking us through her day, McManus recalled: "I set off from Manchester around half seven and drove to Leicester, where Scott lives, with my parents and my other brother to pick up his fiancée and my nieces and nephews.
"When we arrived at his house, he was on FaceTime to his fiancée talking about how he had to wear a suit instead of a tracksuit... I took the phone and told him that if he scored, he would have to do our 'ears celebration'.
We always joke that it's a family trait of having big ears so when he scored and he did it, it was really special."
Still on cloud nine, McManus also said the experience has provided added inspiration for her to achieve similar success with City.
"To see something like that and to see what happiness it brought to my brother is unbelievable," she declared. "I feel I need to repay Scott by letting him see me do something like that.
"When I walked into the stadium, it took my breath away. I was a little bit gutted because I knew we could have been playing there in the FA Cup final but that disappointment just spurs you on to be successful in other competitions.
PICTURE: Scott McManus of @FCHalifaxTown celebrates scoring against @officialgtfc in the #FATrophy Final. pic.twitter.com/QZvtT87dGy— The FA (@FA) May 22, 2016
"Hopefully, I'll get to play at Wembley one day but there is so much to look forward to until then - we have the league, Continental Cup and Champions League."
With Abi and Scott only the latest generation of footballers in the family, it is no surprise the pair have gone on to pursue careers in the beautiful game.
"My mum and dad used to play but not professionally," Abi explained. "My mum's uncle Bob actually went to America with George Best though; he used to play for City. Football has always been in the family.
"If it wasn't for Scott, I wouldn't be where I am today. I used to go along to training with him and his friends, although they are five years older than me.
"I was always trying to get the ball off him so that's where my love of football has come from. I guess I must have taught him something because he's left-footed and the finish at Wembley was with his right!"
Highlighting the increased interest in the women's game in recent years, Abi also revealed she was recognised by the Halifax fans before the match.
She remembered: "When we arrived at Wembley, we sat in a restaurant with all the fans. It was crazy to be honest because people recognised me as Scott's sister and were coming up to me telling me I was doing well.
It was a bit bizarre but it was a really nice feeling to be recognised. They knew Scott was my brother and it made me feel so proud."
Following her memorable day, McManus now has her own must-win encounter to think about - Wednesday's trip to Liverpool.
City sit top of the Super League table, six points clear, and on the back of Sunday's emotional boost, McManus is raring to go.
"I'm back in training now- back to reality after yesterday's dream," she smiled. "Now we're looking ahead to Wednesday's game.
"Hopefully, we can finish just before the break on another win and another clean sheet."