Krug signed a seven-year, $45.5 million contract with the Blues Oct. 9 after nine seasons with the Boston Bruins. He gave St. Louis a 1-0 lead on a slap shot from the point at 13:12 of the first period.
It was the Blues' first power-play goal of the season after failing to score on their first 14 opportunities.
"It feels good," Krug said. "Obviously our power play was not catching any breaks there. We need to work a little bit harder and hopefully now that we've got one, the floodgates will open and we'll feel the confidence to continue to work.
"Hopefully it's the first of many."
David Perron had a goal and an assist, Ryan O'Reilly and Robert Thomas each had had two assists for St. Louis (3-1-1). Jordan Binnington made 21 saves.
"We've got to tighten up defensively, a couple too many turnovers in the D-zone and loose coverage and we've been doing that all year," Thomas said. "[Binnington] has been standing on his head since Game 1 and given us a chance to win every night. We've just got to tighten it up a little bit defensively and 'Binner's' always got our backs."