Miller has wheels, a great shot, and physicality that adds depth to the line, that Lindgren couldn't provide. That isn't to say Lindgren's contributions are negligible, but Miller is more than a great replacement for now.
Mancini will play his 2nd NHL game of his professional career and hopefully be a factor tonight against the Utah HC, who recently beat the New York Islanders, 5-4 in OT play on Thursday.