The loss of Daniel Agger cost Liverpool a shot at the Premier League title last season, according to Rafa Benitez.
The manager's words came as his Danish defender returned to pre-season training at Melwood having missed most of 2007-08 with a metatarsal break.
Benitez told Liverpoolfc.tv: "I think it cost us early in the season. We conceded goals at the end of games which finished as draws because Sami Hyypia and Jamie Carragher were playing too many games in a row.
"We were using Jack Hobbs in some games and Alvaro Arbeloa as a centre-back; clearly we missed Daniel Agger.
"He is a centre-back but good on the ball and a threat for the other team too. We missed Agger."
Benitez tried to sign Gabriel Heinze from Manchester United last summer as cover but the move proved impossible.
Instead Liverpool had to wait until January for top-class reinforcements by the name of Martin Skrtel.
The Slovak made an impressive start to his Anfield career and will ensure that competition is fierce for central defensive places this season.
Benitez added: "We knew this player when he was 18. It was funny because some people were going to see Everton against Zenit and were saying this player really has ability. But we already had four or five videos of him which we liked. We had already sent our people over there and we knew he was the player for us.
"It can be difficult to settle down in this country but Martin has been really good.
"We know the players we want whenever the window opens and we try to sign the players at the right price."