The 50-year-old has already taken Tottenham youngsters Ryan Mason and Harry Kane on loan. However, the Lions boss is eager to create more competition for places in the side ahead of the second half of the season.
"We need to change it round," he said. "I do think that.
"Kane is an addition for us, and there have got to be other players to come in to compete for those positions.
"We do okay in most games, we don't get outplayed and we don't get outclassed. But to strengthen the side is a priority."
Millwall are currently two points outside the relegation places in the Championship.