McCallum made the most of his opportunity to shine by scoring with a powerful header, while Potts was the only Hammer to complete the full 90 minutes at Turner's Cross.
Speaking to West Ham TV, the two teenagers were happy to have been given the chance to get more first-team minutes under their belts in Ireland. For McCallum, his goal marked the end of a whirlwind week that started with him training with the Under-21s at Chadwell Heath.
"Yes, I started the week with the 21s and didn't think I had a sniff of coming out here," confirmed the 19-year-old forward. "I got a phone call during a gym session and had to fly over that night. I came over here and I'm just delighted to be given the chance to show the Gaffer what I can do. I'm even happier that I got a goal."
For the former Dulwich Hamlet youngster, who joined West Ham at the age of 17 in January 2011, the opportunity to train and play with experienced internationals at an overseas training camp is one he relished.
"It's a huge experience for me. I had never been away with the first team before and we never went away in non-league. I'm just delighted to be here."
McCallum's goal arrived in the second half when he rose to nod in fellow youngster Danny Whitehead's clipped cross, and the forward then added an assist by holding off a defender to set up Ravel Morrison.
"To be fair, I tihnk everybody would put their money on me scoring a header. I'd have put my house on it. Then, for Ravel's goal, I showed a bit of pace to get in behind and I've not really got pace! I've out-muscled the left-back, who was only about 5'6, but I'm still buzzing off it! I cut it back for Rav when I probably should have gone for goal myself and got my second."
Potts has more first-team experience than his fellow teenager, having featured ten times under Sam Allardyce, and the England Under-20 defender is eager for more.
With the manager having trimmed his squad ahead of the 2013/14 Barclays Premier League campaign, the left-back knows he and his fellow Under-21s have a chance to stake a claim for a regular place in the matchday squad.
"I'm definitely looking for more. Every year, especially in pre-season, as a young lad you want to set your stall out for the rest of the season. You know, pre-season games are going to give you chances and you have to take those chances to show the Gaffer what you can do and if you're good enough to step up to the Premier League.
"Definitely, this year is a massive year for everyone at the Club."
McCallum knows his physical approach and imposing 6'3 frame make him an archetypal Big Sam forward. With just Andy Carroll and Modibo Maiga ahead him in the pecking order, he is desperate to muscle his way into the first-team reckoning.
"We have only got two strikers at the Club at the moment in Maiga and Andy and I don't know if the manager will sign another one. I've got to watch Andy because he is the main striker here and I've got to do what he does, add it to my game and see if I can get my chance."