The Blues came south looking to heal a sagging game. Instead, they absorbed a blow that carries more precarious implications. Late in the second period of a 2-0 loss to Carolina on Thursday at PNC Arena, winger Andy McDonald fell heavily into the boards and had to be helped from the ice. Slumped over in pain, McDonald favored his right shoulder and did not return. The 34-year-old missed 51 games earlier this season with concussion symptoms. Since a return on Feb. 12, McDonald has been the trigger of the Blues' attack. Before Thursday, he had nine goals and eight assists for 17 points in the 17 games he had played since returning. He also had helped resuscitate an anemic power play. Since the All-Star break, the Blues have the third best power play in the NHL. But the sight of McDonald laboring to the dressing room threatens to end that. "He has a shoulder injury, we'll evaluate him tomorrow," coach Ken Hitchcock said. Hitchcock was frustrated by Tuomo Ruutu's hit on McDonald. "I thought the hit was certainly a penalty; whether it's a suspension or not, who knows," Hitchcock said. The game was still 0-0 halfway through the third period. Carolina has been the poster child of overtime this season, playing extra periods in 18 of 71 starts, winning only three. But a friendly goal by Chad LaRose late in the third — deflected in off defenseman Ian Cole — gave Carolina the upper hand. A goal by Jeff Skinner with 2:38 remaining lowered the hammer.