Despite the absence of Ferguson and the fact that United made 11 changes after their 3-2 Premier League win against Liverpool on Sunday, they cruised to victory at Glanford Park after going a goal down, with Darron Gibson, Chris Smalling, a Michael Owen brace and Park Ji-Sung doing the damage.
"I thought Scunthorpe played their part in a very, very good game," said Phelan. "They created plenty of opportunities, even when we managed to get it to 5-1 I think we'd had about six chances.
"Overall it's a great scoreline from our point of view because it was a new team out there put together in a couple of days, and Scunthorpe should take a lot of pride and credit from the game."
Scunthorpe caretaker manager Ian Baraclough was left to rue his side's bad luck as they found United goalkeeper Tomasz Kuszczak in fine form.
"It could have been so different but it wasn't to be," said Baraclough. "The lads won't be too down about it, I won't let them be.
"Manchester United finished clinically. I've just been told we had 25 efforts on goal, we've made their keeper work 14 or 15 times. I couldn't fault the lads, we just kept going forwards, but we left ourselves open a bit."
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