Roy Hodgson admitted his much-changed Crystal Palace team "capitulated" as they crashed out of the Carabao Cup against Bristol City at Ashton Gate.
Hodgson made 10 switches from the side beaten by Premier League opponents Newcastle three days ago, and City saw them off 4-1.
It was the Robins' third successive win over a Premier League side after eliminating Watford and Stoke, as they moved effortlessly into the League Cup quarter-finals for a first time since the 1988-89 season.
Reflecting on his selection, Palace boss Hodgson said: "I took a risk -- I take responsibility for that. We've had a couple of tough Premier League games and played quite well in both of them, in my opinion.
"I was anxious we rested those players, and I was also very anxious to see some players because a lot of those players out there I've not had any chance to watch in so-called first-team action.
"It was an opportunity for them to knock on the door of the first team and threaten the places of the team I have played in the last two games, so I am bitterly disappointed that didn't work out because there were very few performances that made me think I was picking the wrong team."
More than 2,000 Palace fans made the trip west, and Hodgson added: "I am very disappointed for the fans who came all this way, and I am disappointed by the way at the end we capitulated after at least for the first 45 minutes having had arguably the better of the game.
"We contrived to give away goals at important times, and in the end we are on the back of a heavy defeat."
Palace, the Premier League's bottom club with just one win from nine games this term, led through a Bakary Sako strike, but City never looked back after going ahead before half-time after goals from Matty Taykor and Milan Djuric.
Joe Bryan's rasping left-foot shot on the hour then confirmed Palace's fate in front of a 22,000 crowd, before Callum O'Dowda underlined it six minutes later.
It was a superb response by City to a 3-0 home loss against Leeds last weekend as they once again showcased an exciting free-flowing style.
"It was fantastic," City boss Lee Johnson said. "I will be honest, I thought it flattered us a little bit. They really showed their quality in the first 20 minutes.
"The moment it changed was when Milan Djuric came on. The first moment, he disrupted the back line which let Matty Taylor to get in and get a poacher's goal.
"But then we played really well after that and scored three fantastic goals. You saw the confidence grow then, and Palace were tiring.
"The pick of the [goals] was Joe Bryan's. I was slaughtering him for not crossing it to the back post, and the next thing I see is it is in the back of the net.
"It's a great strike full of power. We see that on a regular basis from him. To win that game against a Premier League side with so many injuries, credit must go to the lads."