Ten Hag, speaking from LA, admits they're eager to add after the arrivals of Josh Zirkzee and Leny Yoro.
He stated: "We already had a very good two buys. So when everyone is fit we have a team who can beat everyone but the squad depth we have to catch up because we had injuries.
"We are vulnerable and we have to avoid this by getting less injuries and second, our squad has to be that good.
"The quality we have in depth we have to catch up but even more because this season will be the survival of the fittest.
"We are looking in all of the positions to reinforce and we are looking for a plan in our squad to reassure ourselves we are always occupied.
"We are occupied (at centre back) but we work continually and the good thing is we already signed two players but I think it belongs to a club as Manchester United that you are always looking if the opportunity is better and we still have time until August 30th."
