The Stanley Cup playoffs have yet to begin and the Dallas Stars already have suffered a huge loss.On the eve of hosting the Colorado Avalanche for Game 1 of the best-of-seven Western Conference first-round series Saturday, Stars coach Pete DeBoer announced top goal-scorer Jason Robertson would be out of action on a week-to-week basis after suffering a lower-body injury in the regular-season finale.”Next man up. It’s this time of year,” DeBoer said. “We’re not going to be the only team either starting without somebody or losing someone at some point. That’s playoffs. You’ve just got to keep moving forward.”Robertson’s injury is a tough blow for a Dallas squad that is also without top defenseman Miro Heiskanen. The Stars finished second in the Central Division, four points ahead of Colorado, but struggled down the stretch and went winless in its final seven games (0-5-2).Somehow, they must find a way to turn their fortunes against a Colorado squad that gained momentum since mid-February.”We’re going to have to,” said forward Tyler Seguin, who returned for the finale after requiring hip surgery in December. “We’ve seen teams do it and we’re going to do it.”Dallas beat Colorado in six games in the second round last season.Adding an extra layer to the series is Mikko Rantanen, whom Colorado traded to the Carolina Hurricanes in January when he and the team could not come to terms on a contract extension. Just before the trade deadline, Rantanen was flipped to Dallas and signed an eight-year deal.”I have a lot of friends off the ice from that team, but I think when the whistle goes on the ice for Game 1, I think then it’s business and we try to beat each other,” Rantanen said. “Business is how I would look at it. Everybody wants to win.”