Marco Silva says Hull need to sign three or four "quality" players before the transfer window closes on Tuesday.
Hull, who have been knocked out of the EFL Cup and FA Cup in the past week, have eight players out injured, while Jake Livermore and Robert Snodgrass have been sold.
Sky sources understand Hull are aware of interest in full-back Andrew Robertson, but will not allow him to leave before the end of the transfer window unless a replacement is signed.
Silva said: "We need to put more players in our squad to change this situation because it is not easy to play all the games and keep players fresh.
"We need to put quality players in our squad. We need three or four players. We will see what happens. We will try."
Hull are second from bottom in the Premier League and face Manchester United, Liverpool and Arsenal in their next three games.
Silva said: "We have tried to do rotation last Thursday and again here but it's not easy with only 15 or 16 players. With this comes problems.
"We've had to use players from our academy, good players, but in this level we need more quality and more numbers.
"To get what we want at the end of the season, to keep this club in the Premier League, we need more players to be competitive in all the moments."