Slaven Bilic hailed West Ham for making their 5-1 FA Cup thrashing of Blackburn Rovers look easy.
Ben Marshall put the Championship side ahead at Ewood Park, but a Victor Moses strike and a fine free-kick from Dimitri Payet had the visitors in front by half-time.
Emmanuel Emenike scored his first two goals for the club before Payet added a brilliant late fifth as Bilic's side took control in the second half following Chris Taylor's red card, though they did see Cheikhou Kouyate sent off in the closing stages.
And the Croatian was delighted with the way his players took control of what had started as a scrappy and evenly contested affair.
"After the first 15-20 minutes, we played really fantastic. We really played great football," he told BT Sport.
"It looked easy, but it's not. Blackburn are a big club. But we made it look a little bit easy – easier than we thought, but only because our performance was really spot on."
Mark Noble believes other teams in the quarter-final draw will now look at West Ham as serious contenders for the trophy following their victory.
"The other teams involved think like that as well," said the midfielder.
"We have players to come in, like Andy Carroll and Diafra Sakho. You also see the options we had off the bench today. It was a tough first 25 minutes. But when we got hold of he game we, got back in it with a couple of bits of magic."
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