Blues coach Ken Hitchcock has altered his forward combinations several times this season, but Tuesday’s changes were notable for two reasons. First, Hitchcock split up center David Backes and right winger T.J. Oshie, who were together for each of the team’s first 25 games. Secondly, he broke up the line of David Perron, Patrik Berglund and Chris Stewart, who combined for eight goals and 10 assists on the recent five-game trip. On Tuesday against the Sharks, one Blues line had Backes with Stewart on his right wing, and another had Berglund center Perron and T.J. Oshie. “We just need different chemistry in other areas,” Hitchcock said. Backes entered the night with one goal in his last 14 games, while Oshie had none in his last 10 and one in his last 14. Meanwhile, Stewart came in Tuesday with four goals and 16 points in his last 15 games. Berglund had four goals in his last four games, and Perron had six points on the recent trip. “I think one of the things that’s really becoming evident right now,” Hitchcock said, “is that we just can’t continue to burden Backes with every part of the game, and then expect him to score goals on top of it ... it’s unrealistic. “I think any of the players in the shortened season that have had that obligation have not been able to contribute offensively, and I think we’ve got to be realistic about that. So if we’ve got to share the wealth in some areas, that’s what we’ve got to do.”