Thomas Frank conceded Brentford "didn't hit our highest level" or "have the cutting edge" as the Bees were stunned by Plymouth Argyle in the FA Cup.

The Premier League side were the highest-profile casualty of the third round, after they were beaten by the Championship's bottom side at the Gtech Community Stadium.

Morgan Whittaker was the hero for Plymouth, who announced Miron Muslic as Wayne Rooney's successor earlier on Saturday.

The forward skipped away from several challenges, before drilling past Brentford goalkeeper Hakon Valdimarsson eight minutes from time.

And Frank was made to rue a lapse in performance levels from his players, who registered just two shots on target with an xG of only 0.41.

"It was a disappointing result and a disappointing performance," the Bees boss told the club's official website.

"You can lose, and then you can lose in a way that's not top - we didn't lose in the best way today because we didn't hit our highest level.

"Congratulations to Plymouth; they did well and they deserved the win. We had the ball a lot, we tried a lot, but we didn't have the cutting edge.

"The way Plymouth defended with structure, with character and with effort made it very difficult for us. That, combined with us not hitting our top level today, was a bad combination.

"They scored a good goal from the guy that we knew could score the goal, which lost us the game."