Latics manager Roberto Martinez, who made six changes for the tie, revealed he only told the 21-year-old he would be in the starting line-up in the morning so he did not spend an anxious night suffering from nerves.
"Callum is such a talented young man, he loves the game and loves playing football and when he started to guess that he was going to be starting he was getting too hyped up," said Martinez, whose side have yet to win in the Barclays Premier League in 2013.
"He would then have a bad night's sleep and we would never be able to get 90 minutes out of him in the previous rounds when he started against Macclesfield and Bournemouth he found it really difficult and I could see yesterday in training he was doing extra work in the gym and I could see he was showing a bit of anxiety.
"So I pulled him over and said I wasn't sure if he was going to start so you can imagine he had a great night's sleep and was a bit angry and this morning when he found out he was playing he was delighted."
McManaman responded with a virtuoso display, clipping home a fine opening goal in the 31st minute and laying on the second which was tapped home by Arouna Kone just before half-time.
The former Everton trainee, who has been with Wigan since 2007, then teed up James McArthur for a brilliant third goal early in the second half as Wigan secured their place in the last eight of the competition for the first time since 1987 and only the second time in the club's history.
Lee Novak pulled one back for Huddersfield with a 62nd-minute header and although the visitors had to withstand a portion of late pressure, they were not unduly troubled and racked up a fourth when Kone smashed home his second in the closing stages.
Martinez added: "I was very pleased with our overall display because I'll never under-estimate scoring four goals away from home against this Huddersfield side, who I've watched a lot in recent weeks and must admit I've been very impressed. We were respecting Huddersfield a lot and I was pleased we played really well as a team.
"We coped with their threat really well, we moved the ball well, kept it well on a difficult pitch and overall did not look like a team who had made six changes and that's the work, that's what we're looking for within the club to develop youngsters that can step into the side and know what they're doing."