The Reds have only signed two players in the summer transfer window so far and both additions have strengthened their attacking department.
Liverpool broke their club transfer record to sign Egypt international Mohamed Salah in a £36.7m deal from Serie A giants AS Roma earlier this month.
The Reds managed to recruit England Under-20 international Dominic Solanke in a free transfer from Premier League champions Chelsea.
The Merseyside outfit were heavily linked with a move to sign Southampton centre-half Virgil van Dijk earlier this summer before publicly pulling out of the deal.
Klopp was forced to use versatile midfielder James Milner in a left-back role last term given Alberto Moreno’s erratic performances.
And speaking to ESPN FC about Klopp’s transfer activity so far, former Liverpool full-back Nicol admitted he was concerned about the lack of defensive recruitments.
“They need to start making a move. James Milner ran his heart out but he’s not a left-back,” Nicol said.
“Dejan Lovren isn’t good enough. Joel Matip can’t stay fit. Nathaniel Clyne is reliable and solid. Simon Mignolet finished the season well but he could be inconsistent again.”
Liverpool finished in fourth place in the Premier League last season to secure a return to the Champions League.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news