Derby manager Frank Lampard has warned his players they can forget about Premier League promotion if they produce a repeat of their dismal first-half display in the FA Cup defeat at Brighton.

County, who are chasing a play-off place in the Sky Bet Championship, found themselves two goals down in Saturday's fifth-round tie at the Amex Stadium following a below-par opening 45 minutes.

A late goal from former England defender Ashley Cole set up a tense finish but the Rams were unable to force extra-time as they lost 2-1.

Lampard laid into his team during the interval and, while he was pleased to see them improve in the second period, insists they must learn from the experience in order to successfully chase a top-six finish.

"It's the best lesson for the players in terms of what we have now, because we have 15 games in the league, all of them so important," said Lampard.

"And if we perform as we did in the second half, we'll have a real opportunity this year.

"If we perform as we did in the first half, then we don't really have that opportunity this year.

"I was very clear in the (half-time) message. I told them in no uncertain terms.

"They're not bad lads, it happens in football.

"I had those performances myself as player, you don't mean to have them but sometimes you walk into them."

First-half strikes from Anthony Knockaert and Jurgen Locadia put Brighton in the quarter-finals for the second successive season.

The Seagulls have been sucked into relegation danger following a six-game winless run in the Premier League.

Albion manager Chris Hughton hopes cup progression will have a positive impact on his team's survival chances.

"We hope that some of this momentum can take us through what has been a difficult time for us in the league," he said.

"At this moment the most important thing for us, however we get them, is getting the points we need."

Seagulls forward Locadia, who claimed what proved to be the winner, later limped off injured and was due for a scan on ankle problem.

With Florin Andone suspended, Hughton could be short of attacking options for the top-flight clash with Leicester on February 26.

"It looks sore, I must admit," Hughton said of Locadia's injury

"We hope he's OK, I don't want to jump the gun but, of course, we know that Florin will be missing the Leicester game, so it leaves us short in that area.

"That is a concern."