Thomas Frank believes referee Chris Kavanagh made a "mistake" in the build-up to Newcastle United's first goal after Tottenham were knocked out of the EFL Cup.

Spurs suffered a 2-0 loss to Newcastle in the round of 16, with Fabian Schar and Nick Woltemade securing the holders’ passage into the last eight.

However, Frank was left frustrated as he believed Schar’s goal should not have stood due to an incident in the build-up.

The defender headed in from a Sandro Tonali corner, but Djed Spence was on the floor putting his boot back on while it was taken, with Spurs protesting for being a player down.

And Frank was equally frustrated by the incident, claiming the small margins ultimately cost Spurs in the match.

"Always disappointing to lose, always disappointing to go out of the tournament that we would love to progress in," Frank told BBC Radio 5 Live.

"Small margins decided the game – it was a very even game with chances and situations in both boxes. The two goals were also small margins where there was two mistakes.

"One [mistake, unfortunately, from [referee] Chris Kavanagh, in terms of things you need to give. Djed Spence had his boot off – he needs time to tie his boot, and he didn't.

"His marker, Schar, scored. I have spoken to Chris about it, and we will keep that between Chris and I."

Spurs finished the match having more shots (11) and double the efforts on target (six to three) than Newcastle, but ultimately failed to hit the target – they accumulated just 0.7 expected goals (xG) from their opportunities.

Frank opted to make just four changes from Spurs’ win over Everton on Sunday but acknowledged it is hard to find a balance amid a busy schedule.

"It was very difficult, to be honest," he said. "You said that Newcastle made eight changes; we made four.

"But I think we made four because we wanted to compete, and I think we competed.

"Unfortunately, we just dropped out on the wrong end of it. So, of course, as you say, it's a busy schedule.

"It's a balance to make a very competitive team that can perform and tactically still hit the criteria we want to hit. We played Everton, four changes, Newcastle, four changes, and then Chelsea on Saturday. Some you need to rest, others you need to be able to perform."