In September 2009, before the start of the 2009–10 season, the Sharks acquired Dany Heatley in a three-player trade that sent Thornton's struggling former linemate Jonathan Cheechoo, left-winger Milan Michalek and a second-round draft pick to the Ottawa Senators. Thornton, Heatley, and Sharks captain Patrick Marleau were joined on the Sharks' top line and enjoyed immediate offensive success together. The trio helped the Sharks to one of their best-ever regular seasons in franchise history. Although the line's production slowed down in the second half of the season, all three Sharks players finished in the League's top 15 in point-scoring. Thornton's 89 points ranked eighth, while Marleau and Heatley finished 14th and 15th in League scoring with 83 and 82 points, respectively. The Sharks entered the 2010 playoffs as the first seed in the Western Conference for the second-consecutive year. After advancing past the Colorado Avalanche and Detroit Red Wings in the first two rounds, the Sharks were eliminated by the Chicago Blackhawks in the Western Conference Finals. Thornton finished the playoffs with a career-high 12 points in 15 games.