Millens View: Watford (a) 1-3
The 24-year-old made his first start of the season against the Hornets and was soon back on the goal trail with a 38 minute equaliser.
Marvin Elliot put the visitors in front midway through the second period before substitute Brett Pitman wrapped up the points in stoppage time.
"You can see the contribution Nicky has made to the team," said Millen.
"He's quick, he's strong and he can finish.
"I wanted to start him and for him to last 75 minutes is a great effort. I certainly thought he had 45 minutes in him but he didn't look rusty.
"He scored his goal and showed his quality and his movement on a difficult pitch. Hopefully he's okay for Saturday."
Bottom of the league Scunthorpe visit Ashton Gate at the weekend and Millen wants more of the same from his side.
He added: "To win games we've got to be solid. At home we tend to go all out and too often we've been caught on the break.
"We've got to learn from tonight because we were solid and we were able to benefit from the pace of the players up front.
"It was a team effort, the lads defended for their lives.
"We're a good side on the counter attack with good pace out wide. When we get the ball wide we can score goals."