While Dyche accepted the challenge may have been permissible in years gone by, he insisted that is no longer the case by modern standards as he criticised the officials' performance and their decision not to reprimand Robinson.

Dyche said: "In my day that was standard and every week, but nowadays it's unacceptable. The linesman is four or five yards from it and gives nothing, the ref gives nothing and we haven't got VAR.

"If you look at it back, it would be a card in anyone's book.

"I thought it was a bizarre game from the officials, one minute they're giving (a free-kick) for a tiny touch in the back and then that challenge, it was almost nothing. A foul and that was it.

"You're scratching your head when you see it back. Having seen it back, it's a really bad challenge, he should have been red-carded."

Dyche admitted he would be surprised if it were only a minor setback for Gudmundsson, who made only 13 appearances in all competitions last season due to hamstring and calf injuries.

Burnley are already low on numbers, with goalkeeper Joe Hart and midfielders Jeff Hendrick and Aaron Lennon leaving on free transfers over the summer, while centre-half Ben Gibson has been allowed to join Norwich on loan.

Dyche said: "We're trying to protect people here because the Premier League is the be-all and end-all at the moment, not because we don't want a cup run. We respect all the competitions but it's just a logical fact.

"It's very difficult at the minute, we haven't got enough players, we've lost another one. (Johann) has twisted his knee, at this stage it's unlikely it's going to be a matter of days, I'd be very, very surprised.

"Unfortunately there's not a lot in the pipeline, I don't know anything that is, so it's going to be tough."

James Tarkowski, who has been the subject of three failed bids from West Ham and is also reportedly attracting interest from Leicester, was a notable omission from Burnley's starting line-up because of a toe injury.

Dyche is hopeful he will be available to face Leicester on Sunday, as he said: "We don't think it's serious, it was more of a jarring sort of thing into the new end of a pair of new boots which just got too sore."

As for how they fared against the Blades to set up a third-round visit to Millwall, Dyche added: "I thought overall the performance was very good, individually and collectively."

Sheffield United made 10 changes to the side that lost to Wolves in their Premier League opener on Monday and Wilder was encouraged by the performances of those who played.

He said: "I don't want this to be an easy season for me as a manager in terms of picking that side. Everybody had that opportunity to impress and they've certainly done that.

"We're disappointed that we've not gone through, it's fine margins and we go again. We're in good spirits, there's not a lot wrong with us."

As for Robinson's challenge on Gudmundsson, Wilder added: "It's unfortunate. I've not seen it back. I've been told that it may have been a little bit near the mark, it's just trying to get that balance right."