Jones, who had earlier netted his fifteenth goal of the season to give the Bantams the lead on the final day of the regular campaign, limped off in the second period at Rochdale's Crown Oil Arena after tweaking his hamstring.
It was initially felt that the forward had little or no chance of featuring in either leg of City's semi-final with Fleetwood, but McCall says Jones' hopes of featuring have now improved after a positive response from the 22 year-old.
McCall said: "It is looking far better than what I first thought it would be for Alex.
"It didn't seem too much of a stretch at the time, and he certainly seems to have improved dramatically over the last 48 hours or so.
"He doesn't have any real pain in the area now but we will monitor him tomorrow (Wednesday).
"If it is too big of a gamble for Thursday (first leg), we will be hopeful for Sunday (second leg) instead.
"If he is pain-free tomorrow, however, and showing no adverse effects, then he could still be involved for Thursday.
"After the (Rochdale) game, I'd ruled him out in my mind, especially knowing how hamstring injuries can be like. But he has a great chance for Sunday and a good chance for Thursday if he keeps improving the way he has been doing."
With City continuing to assess Jones' injury situation, the fit-again duo of Matthew Kilgallon and Alex Gilliead are expected to be in the shake up for a place in McCall's match-day squad on Thursday after coming through last Sunday's game with Rochdale unscathed.
McCall added: "Killa (Matthew Kilgallon) did fantastically well to get through 95 minutes in total at Rochdale.
"Alex Gilliead coming back in the game as well was also a bonus.
"Both got through the game fine, both have trained fine today (Tuesday), and both are fit and raring to go for Thursday if called upon.
"We have some big decisions to be made over the starting line up and the bench because we had some good performances on Sunday."