Motherwell manager Stephen Robinson backed Christopher Long to go all the way to the top after the striker's hat-trick propelled his side into the fifth round of the William Hill Scottish Cup.

Long struck from a deflected free-kick, finished off a cutting move in style and added a third from long range following a mistake by Dundee goalkeeper Jack Hamilton to earn Motherwell a 3-0 win.

Robinson said: "Chris Long can go to a really good level if he really believes in himself.

"We are constantly on at him, we have a coaching staff that constantly work on people to make them better and we are trying to get Longy to believe he is as good as we think he is.

"He is a boy who can keep getting better and better.

"He needs to keep playing football. He is a boy who hasn't found a home yet, so maybe he's found one here."

Motherwell were two up by the half hour and Long rounded off the win in the 75th minute after Dundee had made a game of it after the break with Kane Hemmings heading against the crossbar.

Robinson said: "When you look at their 11, they have a lot more Premiership experience than us. We are still a very young, naive squad, so to come away with a 3-0 victory – and it probably could have been more.

"First-half performance was good, we started a little bit sloppy in the second half and gave Dundee a little bit of ownership of the game because we went too long, too early."

Dundee manager James McPake bemoaned their poor start.

"It's easy to come out in the second half and have a go when you are 2-0 down," McPake said.

"We didn't start the game well enough, it was the same old problem, and the difference was we were up against a really good side who can hurt you.

"We have got to be better, individually and as a team, we have got to be better all over the place."