Frankfurt were promoted back to the top flight of German football after a one-year absence last season, but Veh says they will be going straight back down again if he does not get a solid backbone to his side.
"I think I have got some good guys so far, but we certainly need another three central defenders," he said.
"We all agree that you cannot win games in football without a defence. If we did not know that, then we may as well all give up now."
Frankfurt have sold one of their central defenders, Gordon Schildenfeld, this summer, leaving only Heiko Butscher as a fit, recognised centre-back on their books.
Martin Amedick is currently signed off for an indefinite spell due to burn-out.
"We have got may young, talented players who we can really improve, but only on the condition that I get my central defender," he added in the Suddeutsche Zeitung newspaper.