Liverpool manager Jurgen Klopp has clashed with former player Jamie Carragher over the club's transfer business this summer.
"There are question marks now about Joe Gomez. So there is no doubt that Liverpool had to go big in the transfer market."
The next day, Klopp responded to the comments in a news conference ahead of Liverpool's Champions League opener at Ajax on Wednesday.
"We went into the season with three centre backs plus Fabinho as cover and some youngsters," Klopp said. "It's hard to have four world-class centre halves.
"If anyone wants to tell us we made a mistake -- I think Carragher mentioned already -- there are a few reasons why they don't do this job."
Carragher replied to Klopp's criticism on social media and wrote: "Not once this season have I said it was a mistake for Klopp not to buy a CB for the exact reason he states."
Van Dijk is set to undergo knee surgery and faces a lengthy period on the sidelines.