SKC took the away leg 2-0 on the weekend before repeating that scoreline at home thanks to goals from Aurelien Collin and CJ Sapong either side of half-time to record a 4-0 aggregate win.
"You're not in the postseason by luck, you're in there because your record and your form suggests you're a good team," Smith said. "And this Kansas City team is a good team."
And Sporting midfielder Graham Zusi, who supplied the two free-kicks which were headed home by the aforementioned goalscorers, feels the team is in great shape for whoever they meet in the next round of the play-offs.
"It's been that hot team in the playoffs that usually makes a good run of it," Zusi said. "That's what we are right now. We're a hot team, and we're tough to beat right now."