The young Gers led their Belgian opponents for the majority of the contest, but a ten-minute spell late in the second half deprived the away side of a positive outcome.
Speaking to the official Rangers website after the match, McCallum reflected: “It was an excellent game for us for the first 70 minutes, in terms of managing the game.
“Antwerp had a decent amount of possession, but I thought our structure out of possession was fantastic.
“We made it difficult, plugged a lot of spaces that they wanted to access, and off the back of that we had some real good moments in possession.
“The only frustration at half-time was that we had only scored the one goal, which comes from an excellent through pass from Bailey Rice and a great run through from Josh Gentles.
“We started the second half really well and scored an excellent goal through Findlay Curtis.
“We lost a goal on the 70th minute mark which was controllable from our side, and then a quickfire two goals off the back of that which was really harsh on the lads based on the first 70 minutes.”
It proved to be a tough lesson for Gers B side – which contained only one player over the age of 19 – to stomach after pouring so much into the game.
However, McCallum believes exposure therapy will benefit his players, insisting the nature of the game underlined what it takes to compete over 90 minutes against continental opposition.
He continued: “We’ve experienced it before, but the more exposure that these lads get to these types of games, the more comfortable they will become in these environments.
“The other bit they can take from it is that 70 minutes isn’t enough. The game goes to 90 minutes. For that final 20 minutes, we switched off in key moments and didn’t value certain aspects of our defensive roles.
“When you lose a goal, the mood can become affected, and sometimes you start to put yourself on the back foot a little bit and the other team get a lift.
“Goals can change games, and unfortunately in that spell we weren’t at the level that we were in the first 70 minutes.”
On Zak Lovelace, who was withdrawn early in the first half, McCallum added: “He felt a little bit of tightness. It was a bit of a precaution, and we don’t want it to become something more than it is.
“He very quickly put his hand up and said that he felt a bit of tightness, so the medical team rightly made that decision.”