Simpson watched on as a brace from impressive 16-year-old Connor Wickham and a further strike from Alan Quinn was matched by efforts from Jake Robinson, Dave Hibbert and Shane Cansdell-Sherriff.
Shrews held the Tractor Boys to a 3-3 draw before the Championship outfit finally prevailed 4-2 in the shootout following a goalless extra-time period.
Simpson said: "After Saturday's performance we were even better but we also learnt that if you give players from a higher league room you'll get punished.
"Wickham looks like an outstanding prospect. I'd like to check on his passport, I can't believe he's only 16."
Source: Team_Talk