The 40-year-old forward is the leader among active NHL players in assists (1,075) and points (1,488). One category he's not even No. 1 on his own team in is games played; Thornton is 87 games behind longtime Sharks teammate Patrick Marleau, who will be playing his 1,687th game, fifth on the all-time list.
Here are some of the key dates and milestones in Thornton's NHL career:
June 21, 1997 -- The Boston Bruins select Thornton, a center with Sault Ste. Marie of the Ontario Hockey League, with the No. 1 pick in the 1997 NHL Draft at the Civic Arena in Pittsburgh. Boston takes Thornton after he finishes his second season in the Ontario Hockey League with 122 points (41 goals, 81 assists) in 59 games.
Oct. 8, 1997 -- Thornton makes the Bruins out of training camp but is scratched for Boston's first three games before making his NHL debut in a 3-2 win at the Phoenix Coyotes. But he rarely sees as much as 10 minutes of ice time, and it's not until Dec. 3, his 22nd NHL game, that Thornton gets his first point -- a goal against the Philadelphia Flyers. His first assist comes against the Washington Capitals on Jan. 25, 1998, and he finishes his first NHL season with seven points (three goals, four assists) in 55 games.
Oct. 8, 2002 -- Exactly five years after making his NHL debut, Thornton is named captain of the Bruins. He responds with his first 100-point season, finishing with 101 points (36 goals, 65 assists) in 77 games. Despite Thornton's production, the Bruins drop to third place in the Northeast Division after finishing first in 2001-02, then are eliminated by the New Jersey Devils in five games in the first round of the Stanley Cup Playoffs.
Aug. 11, 2005 -- Thornton, a restricted free agent after a 2003-04 season that ends with him going scoreless in seven games against the Montreal Canadiens during a first-round upset loss in the Stanley Cup Playoffs while playing with torn rib cartilage, signs a three-year contract with the Bruins.
Nov. 30, 2005 -- Though Thornton gets off to a hot start (33 points; nine goals, 24 assists in 24 games), the Bruins do not. They trade him to the Sharks, receiving defenseman Brad Stuart and forwards Marco Sturm and Wayne Primeau.
April 17, 2006 -- Thornton is held scoreless by the Los Angeles Kings in San Jose's final regular-season game but finishes as the NHL scoring leader with 125 points (29 goals, 96 assists), becoming the first player in League history to win the scoring championship while playing for two teams. Two months later, he becomes the first player voted as winner of the Hart Trophy as NHL MVP after playing with two teams during the same season.
April 7, 2007 -- After a slow start largely attributable to a toe injury, Thornton gets hot in the second half and finishes with 114 points, second to Sidney Crosby of the Pittsburgh Penguins in the NHL scoring race. Thornton does lead the NHL with 92 assists, including two in each of San Jose's final two games. He becomes the third player in League history to have back-to-back 90-assist seasons; the others are Wayne Gretzky and Mario Lemieux.
Feb. 28, 2010 -- Thornton, part of Canada's non-medal winning team at the 2006 Torino Olympics, earns a gold medal when Canada defeats the United States 3-2 in overtime at the 2010 Vancouver Olympics.
Oct. 7, 2010 -- One day before the Sharks start their season against the Columbus Blue Jackets in Sweden, Thornton is named the eighth captain in team history. Nine days later, he signs a three-year contract that will keep him in San Jose through the 2013-14 season.
April 8, 2011 -- Thornton becomes the 78th player in NHL history to reach 1,000 points when he bats the rebound of Logan Couture's shot out of midair and into the net against the Phoenix Coyotes. Point No. 1,000 (306 goals, 694 assists) comes in Thornton's 994th NHL game. He also reaches the 20-goal mark for the 11th consecutive season.
Oct. 21, 2011 -- Thornton is the 266th NHL player to reach the 1,000-game mark when he steps on the ice for the Sharks against the New Jersey Devils at Prudential Center. He scores a goal and assists on another in San Jose's 4-3 shootout win.
Aug. 20, 2014 -- The Sharks take the captaincy from Thornton four months after San Jose becomes the fourth team in NHL history to lose a Stanley Cup Playoff series after winning the first three games. The Sharks play the 2014-15 season without a captain. Joe Pavelski is named captain for the 2015-16 season, with Thornton selected as an alternate captain.
Jan. 27, 2015 -- Thornton becomes the 33rd player to reach 1,300 points in his NHL career when he has two assists in San Jose's 6-1 win against the Colorado Avalanche at SAP Center. He also extends his point streak to 10 games; it's Thornton's longest since a 10-game streak from Nov. 14 through Dec. 3, 2009.
March 19, 2015 -- Two assists in San Jose's 4-1 win at Toronto give Thornton 900 in his NHL career. He's named the game's First Star.
May 30, 2016 -- Thornton plays in the Stanley Cup Final for the first time when the Sharks take the ice against the Pittsburgh Penguins at Consol Energy Center. His hopes of winning a championship end when the Penguins win the series in six games. Thornton finishes the series with three assists, giving him 21 points (three goals, 18 assists) in 24 playoff games. One week later he's named an NHL Second-Team All-Star after averaging a point per game during the regular season (82 points; 19 goals, 63 assists in 82 games).
March 6, 2017 -- With an assist in San Jose's 3-2 win against the Winnipeg Jets at MTS Centre, Thornton becomes the 13th player in NHL history to have 1,000 in his career. He reaches the milestone with an assist on Joe Pavelski's empty-net goal with 26 seconds remaining.
Nov. 13, 2018 -- Thornton's 400th NHL goal gives the Sharks a 5-4 win against the Nashville Predators at SAP Center. He becomes the seventh player in NHL history to play 1,500 games, score 400 goals and have 1,000 assists.
Video: NSH@SJS: Thornton nets 400th goal to put Sharks ahead
Jan. 16, 2019 -- San Jose defeats the Pittsburgh Penguins 5-2 in Thornton's 1,000th game with the Sharks. He celebrates by scoring a goal, a one-timer that cleanly beats Pittsburgh goalie Matt Murray and proves to be the game-winner.
Video: PIT@SJS: Thornton scores in 1,000th game as a Shark
Feb. 7, 2019 -- Thornton becomes the second player to have 1,000 points as a member of the Sharks. Appropriately, the milestone point is an assist -- a highlight-reel pass that sets up Evander Kane's first-period goal in San Jose's 5-2 win at the Calgary Flames. Thornton trails only Marleau (1,082 points) on San Jose's all-time scoring list.