The Scotland centre-half played the full 90 minutes in Tuesday's 1-0 win at Birmingham as Wigan booked their Championship play-off place with one game to spare.
Caldwell, who made a substitute appearance in the FA Cup semi-final penalty defeat by Arsenal, had been sidelined since last May after undergoing a hip operation.
But the 32-year-old now looks set to play a major role in Wigan's bid to bounce straight back to the top-flight via the play-offs.
"It's obviously good for me; it's been a lot of hard work in the gym, out on your own working with the physios and the fitness coaches and it can be very difficult. It's nice for that hard work to get rewarded with a win and a clean sheet when I come back in and I hope for more between now and the end of the season."