Walter Mazzarri said Watford did not deserve to lose against Millwall in their FA Cup fourth round tie.
The Hornets, who made seven changes for the game against the League One side, have only won once in nine games to intensify the pressure on Mazzarri, but the Italian was adamant his side were hard done by.
"I will speak with the players face-to-face [on Monday]," the Italian said. "We didn't deserve to lose. If the referee [Martin Atkinson] had given us a penalty in the second half [for a challenge on Stefano] Okaka it would have been a completely different game.
"I'm very disappointed, angry and sorry for our fans. It seemed we were never going to concede but we ended up conceding.
"A lot of players have been missing but slowly we're getting them back. This is also the reason we had to change [the team]. I want a team that in the next 16 games [until the season's end] fights for every ball."