Last year saw the club’s under-19 side fall at the first hurdle in a 3-1 extra-time defeat to Dundee United at Ibrox.
That ended a run that had seen the Light Blues reaching five consecutive Hampden finals in the competition.
It was a massive disappointment for everyone in the club’s youth department, but the progress of both Barrie McKay and Lewis Macleod from the under-19 team that day to the first team now is what Sinclair is most proud of.
He said: “That’s success for us. They have done very well and I hope they continue to do well for the manager during the course of the year.
“We were bitterly disappointed with that result last year because we had a group that we thought would have done better and it was a result from which we never really recovered.
“But we’re not really here to produce teams as everyone should be aware. We’re here to get players in to the first team and it really is a bonus if the sides do well at that age.
“Reaching finals is good for their education, but the bottom line is that we need to try to get players ready for the manager to support and complement the first team squad.”
That has continued to happen for the Light Blues with a number of youth team graduates reaching the first team over the past few seasons.
And with Sunday’s side against St Johnstone likely to be shorn of eligible players like McKay and Macleod who will travel to Berwick with the first, it is something Sinclair hopes to see continuing.
He added: “If I had the choice, this is the way it would be. If we had a full complement of youth players and none in the first team squad I’d be bitterly disappointed.
“We have Barrie, Lewis and Robbie Crawford, I suspect, with the first team and also Kamil Wiktorski who may travel with the squad.
“That’s success for us though. That will be one glimmer for us at the end of Sunday if the result doesn’t go well, the fact that we’ve had kids in the first team squad.”
Kick off on Sunday is at 1pm at Ibrox. You can pay at the gate, £4 for adults and £1 for concessions/juveniles.