"When you've got players like Nicky Law and Keith Lasley . . ." he said. "These guys are different class every week, the standard they play at is exceptional. Even if you play well, you know for a fact when they're fit they'll get back in the team."
Law, though, has now moved on. And with Father Time harrying certain others across the pitch, might there be an opportunity for young talent like Carswell to stake a claim for the considerable future? "I think if you could come to training to see how fit Las is, you'd be surprised," he laughed. "Not that he's who we're talking about, right enough . . ."
So important is Lasley to the club that Motherwell's teamsheets probably come pre-printed with the captain's name already inked on. He is very much the big cheese, the first cab off the Merry Street rank; the lead soprano - although opposing players might argue his crunching tackles are more reminiscent of Mafia boss Tony than Maria Callas. For a young player coming through the youth set-up, though, having guys with that kind of experience around is priceless.
"It's not just Lasley," Carswell said. "You've got Steven Hammell, [James] McFadden, [Stephen] McManus . . . the level they've played at over the years, they know how everything is and you learn a lot from them."
Despite the presence of midfield heavyweights in front of him in the pecking order, Carswell never considered moving on to find first-team football and his perseverance paid off in the summer when Motherwell's summer exodus left expanses of the playing area up for grabs. "You've got to wait and play a few games before you look to go somewhere else," he insisted. "Last season, I thought about a loan, but I'm still young and I was involved in matches, coming on as a sub. I don't want to be chapping on the gaffer's door to go out on loan when I'm in his plans. And, right enough, whenever there were injuries he was giving me a chance."
Stuart McCall, his manager, gave Carswell his debut in a cup run a few years ago, but it is this season's whirl at a trophy which has excited the Fir Park faithful, after Celtic followed Rangers in being dumped out of the Scottish League Cup on Tuesday. "The cup is anybody's now," Carswell admitted. "It's up to us to show up against Aberdeen - they've put us out the last few times, so it's up to us to go out there and show what we can do."
"We wanted a home tie," confirmed a pleased McCall. "It's a difficult game, don't get me wrong, but anybody away would have been difficult. It's an exciting competition, all the ties have got an edge to them."
He steered the conversation towards more pressing concerns, namely the threat posed by Ross County this afternoon. "I'm sure they'll come in great heart after that comeback [against Hearts] last week; we'll need to be at our best to continue our [unbeaten] run. Derek [Adams] has chopped and changed at the back. They lost four goals a couple of times, and he's looking to shore things up a little bit. He's brought [Scott] Boyd back in who did terrific last season. I'm sure once he gets his players gelling they'll have a good season."
And indeed Adams is satisified with the progress he has made so far in that quarter. Last week's air-punching last-minute victory made it seven points from four league games for County since they lost their first three matches of the season.
Adams had faced one of the toughest post-season rebuilding jobs this summer, mostly because two of his best players in Iain Vigurs and Paul Lawson defected to Fir Park and could line up against their former side tomorrow. But the County manager was boosted by summer signing Melvin de Leeuw's impact from the bench last week as the Dutchman scored the equaliser and set up Richie Brittain's winner.
"Year on year you have to change the team, that's just the nature of the business and where we are location-wise," Adams said. "We have taken in nine players and lost nine players. It takes time for players to adapt. We have taken in a number of foreign players and it takes time for them to adjust.
"We have taken seven points from the last four matches and played really well. It's going to be tough but we are enjoying it. We are scoring goals, but we have to be a wee bit tighter at the back."