The 23-year-old Tigers tighthead again impressed on the tour to Australia and New Zealand and Johnson is thrilled with the progress of his pack.
Fellow new-boys David Wilson and Paul Doran-Jones will keep Cole on his toes and Johnson said: "Where was Dan this time last year? He has come on tremendously.
"With Davey (Wilson) and Paul Doran-Jones, the tightheads will all have to travel home on separate planes.
"We have now got a powerful scrummage at that level. Steve Thompson has come back and is a big powerful man in the scrum. Tim Payne played some of his best rugby for England over the last two Tests.
"We have the best depth at loosehead where Dave Flatman has done a very solid job. Jon Golding has been hampered by injury but he looked really good in flashes."