Mohsni played for former club Southend in the Johnstone's Paint Trophy final against Crewe at Wembley last year.
His family and friends travelled over from France to see him in action and over 40,000 fans crammed into the famous stadium.
But he had a shocker, missed an absolute sitter and was substituted by his manager Phil Brown after less than an hour on the park.
The player had to look on from the sidelines as his League Two side slumped to a 2-0 defeat to their League One opponents.
The centre-half is set to play for Rangers against part-time minnows Albion Rovers in the Scottish Cup quarter-final at Ibrox on Sunday. And he revealed that he is keen to help them progress so he can atone personally for his failure in his only other outing in a major final.
He said: "I lost in the final of the Johnstone's Paint Trophy last year which was sad. I was looking forward to playing in it, but when I did I was rubbish, completely rubbish.
"I was substituted before we had played an hour and I didn't have any excuses. I didn't help the team at all.
"I had a chance to score that their goalkeeper saved. Crewe played better than us and deserved to win.
"It was such a shame because this was a game that was so important for the club, the fans and the staff.
"I played central midfield at Wembley, right in the middle of the pitch. But it would have been as much good if I had been running around the outside of it!
"That was the most disappointed I have felt after a game, for sure. After that, it is the feeling when you get a red card."
Mohsni added: "On Monday after the final we watched a video back. It was 15 minutes long - and 14 minutes of it was of me! I was rubbish.
"It was difficult because when you play central midfield, you need a good relationship with your centre-backs so they know when you want the ball and when you don't.
"We didn't have that understanding. It was a nightmare game.
"I was so happy to play at Wembley, too. The final of the Champions League was going to be there afterwards so it was like: 'Wow!'
"My friend and my brother both came over to the game, so the build-up was very exciting. But it wasn't a good game for me.
"I had been injured that season and maybe wasn't match-fit. You can make excuses, but I was just rubbish.
"Lee McCulloch and the Scottish players here have emphasised how important this competition is. I can compare it to the French Cup, which is also very important to win.
"It would be great for the fans, the club and the staff - and for me, too. I'd be very happy to win it after having such a bad experience at Wembley last year."
Many Scottish football fans are interested to see how Rangers perform against an SPFL Premiership club if they make it through to the semi- finals of the Scottish Cup.
ALLY McCOIST'S men played three times against top-flight opposition in cup competitions - they beat Motherwell but lost heavily to both Inverness Caledonian Thistle and Dundee United.
However, the 2012/13 campaign was, despite winning the Third Division title, a difficult one for the Ibrox club due to their much-publicised off-field problems.
Their manager strengthened considerably during the summer by bringing in free transfers like Cammy Bell, Nicky Clark, Jon Daly, Richard Foster, Nicky Law and Mohsni.
And they are unbeaten in the third tier - albeit against mainly part-time teams - this term and are still involved in both the Ramsdens Cup and the Scottish Cup.
Mohsni believes Rangers could give the Premiership teams still involved in the competition - Aberdeen, Dundee United, Inverness and St Johnstone - a game if they progress to the last four.
He said: "I don't think we're favourites for the Scottish Cup. There are other Premiership teams who deserve to be favourites more than us.
"But in a cup any team can beat any other team. Every player in our squad would like to face a Premiership team to see what we can do against them.
"That's what we're looking for in the next draw if we get through this round on Sunday."
Mohsni and his Rangers team-mates can sew up the League One title against either Airdrie on Wednesday night or Dunfermline on Saturday week.
When they finally complete Stage Two of "The Journey" the defender believes they will be keen to maintain their undefeated run until the end of the season.
BUT the French-Tunisian player feels that having the Ramsdens Cup final - they take on Raith Rovers at Easter Road in April - and the Scottish Cup to focus on will help them.
He said: "We only need two more games to win the league. After that's over we can concentrate on two cups. The Scottish Cup is one of the best so it would be good to win it and play in the semi-final at Ibrox again.
"It will keep us concentrated. We want to win the league unbeaten and every player in Scotland wants to win this cup.
"Would I rather go the season undefeated or win the Scottish Cup? Well, I would lose a couple of games and win the cup.
"We maybe have two more games to win to get the league. So we can win those two games - then after that lose every game and win the Scottish Cup!"
Mohsni was speaking to promote the Rangers Charity Foundation's partnership with Unicef.
The Foundation is bidding to fund up to one million vaccines by 2015.
Mohsni said: "I am a huge fan of the life-changing work Unicef is carrying out in areas where children are at enormous risk of dying from preventable illnesses.
"The Rangers Charity Foundation prides itself on being able to make a difference to individuals in need. It is an honour to be involved in such a vital and exciting partnership."