The Millers striker opened his campaign for the season in fine style on the west coast, sending in a swerving effort from 25 yards in the second half.
That was enough to earn Warne's side the win, but will also have drawn attraction from possible suitors.
Smith has been one of the key players at the AESSEAL New York Stadim over the last few years and has had to watch as the likes of Will Vaulks, Semi Ajayi and Matt Crooks have all earned big money moves.
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“I told Smithy to pass it,” Warne said of his goal.
“Ollie (Rathbone) did really well, I thought he looked good, he was always looking forward and he got the ball into Smithy, I thought he was going to have to play it off, but he has hit it and it was a screamer.
“His efforts are pretty phenomenal at the club. Everyone knows what he does but he probably doesn't get the goals that his play deserves so for him to score a goal like that I am really chuffed.
“I spoke to him earlier, he has seen players leave this club all the time and he always seems to be the last toy on the shelf, but if he keeps scoring goals like that he is going to be difficult to keep hold of.”
The Millers overcame a difficult opening in tough conditions on Tuesday to bounce back from their defeat at Wigan on Saturday.
“In very difficult conditions, there is no easy games in any leagues, we didn't under-estimate them, we knew we had to battle,” he said, “In the first half, we didn’t have enough care in the final third.
“I asked them at half-time to take an extra pass and I thought we were a lot better in the second half. I thought we deserved our win, truth be told.
“We were professional at the end, ran the clock down in the last five or 10 minutes, which in 16 years at the club I don't know I've ever seen.
“Overall, I was pleased with the performance. We played a different team tonight, all of the lads are going to play a massive part.”