However, VAR overturned the decision and Heung-min Son converted from the penalty spot.
Speaking afterwards, Smith said: "I don't get it! There were 40,000 people in this stadium today and Martin Atkinson gives a goal kick and everyone in this stadium gives a goal kick. Even their player who had the shot.
"We go into a sterile environment and whoever the VAR is today looks at it 10 times, you're telling me that's clear and obvious? The criteria is clear and obvious.
"I said to Atkinson at half-time, I don't blame you but if you're brave enough to walk over to that monitor. It takes 30 seconds to look and say I'm happy with my decision, we play on.
"But, instead, we go upstairs and have it refereed. If you look at it 20 times, you're going to see contact. Was it contact that put the lad off? Not sure. The criteria is clear and obvious, that's not clear and obvious. Because there was contact before, that'll probably put their marks up to 98 per cent. For me, it's farcical."