The new faces can also prove they belong on a stage that is likely to attract the largest attendances in League One this term.
“You never know how a player handles situations until they are here,” said McCall, when asked about the prospect of playing in front of bumper crowds every other week.
“For Shay McCartan, it will be different playing in front of 18,000 compared to 1,800 at Accrington.
“That is a fact of life. I saw it when I went to Rangers. Not so much myself because I had played for Everton at Goodison Park but there were others who came in from elsewhere in Scotland and it was a big leap.
“Duncan Ferguson was at Dundee United when he came in. It is only when you are then in front of 50,000 and the expectation levels are so high that you appreciate the difference.
“We do all the background checks we can but it is only when they are in the building that you truly now. What I will say is I have full confidence in these lads.”
McCall’s task in pre-season has been to blend together a squad that saw several high-profile departures in the wake of losing the League One play-off final.
“Our job is to improve the players and I think that is one thing myself and Kenny (Black, assistant) have done very well together,” he added.
“The lads from last season who left, if they didn’t move up a league – like Mezza (James Meredith, who joined Championship Millwall) – then they doubled their wages or even more. That suggests they all improved as players while playing under us.
“As the lads moved on, myself and Kenny got messages and texts thanking us for what we had done. That was nice.
“Our strategy is to get them in and help them learn. And, ultimately, succeed. The biggest part of management is recruitment and, nowadays, I get a lot more help. In my first spell here (between 2007 and 2010), it was basically doing it yourself. Agents would come to me direct and I would then have to check the players out.
“But, now, with Greg (Abbott, head of recruitment) on board, the workload is spread. Greg helps out a lot, as does Edin (Rahic, vice chairman). Recruitment is key and then it is all about man-management. Once the window closes, it is our job to get the best out of what we have.”