The head coach of MLS expansion franchise Philadelphia Union has issued a friendly warning to his players - things will get tougher.

Peter Nowak was just content with the Union's first official exhibition match - a 5-0 victory over the University of North Carolina - but says there is a lot more hard work to be done throughout pre-season.

"I wasn't really happy with the first 20 minutes on Saturday," he admitted.

"We need to start in better fashion than we did on Saturday, regardless of the result at the end.

"The agenda is to build on what we are achieving here. Of course, the soccer part needs to be really expanded," Nowak added. "More soccer information, more structure, more discipline, more emphasis on the soccer part.

"We need a team discipline structure and we need to work on that. At the end of the MLS season you've got to be mentally strong. The camp was long, the camp is hard.

"They are working very hard and the work ethic has been great, but now is the mental strength and you've got to pull it through. You've got to fight your weaknesses, your fears, your doubts and that's what I was not happy with.

"This must improve in the course of any training camp."