A first-half Shane Long effort and late strikes from Ian Harte and Noel Hunt put the Royals in command before Connor Wickham netted a late consolation for the Tractor Boys.
"We were so flat it was unbelievable and looked leggy and tired. Reading were better than us in all areas and we were soundly beaten," said Jewell.
"Losing Jimmy Bullard (to a hamstring injury) was a huge loss but there just wasn't any spark in the team. We were second to every ball and didn't put them under any pressure, whereas they always looked a threat.
"We've got to do better but I'm not going to slate the players because in the main they've been terrific since I've been here. Sometimes you get performances like that and you don't know where they come from.
"It was so quiet out there. It was like a reserve game. There was no zip or zest from anyone and I'm at a loss to explain it. It was a terrific goal from Connor (Wickham) but we need someone to do that when it's 0-0."
Source: PA
Source: PA