Rielly entered the NHL with the Toronto Maple Leafs to much fanfare, which is to be expected with a big, skilled, swift-skating defensemen who can drive the offense on the power play or at even strength.

The 6-foot-1 Vancouver native was selected by Toronto with the No. 5 pick in the 2012 NHL Draft; he might have gone higher if not for a knee injury that limited him to 18 regular-season games in his draft year with Moose Jaw of the Western Hockey League (he returned from surgery during the WHL playoffs that season).

Given Rielly's play after the draft, it's doubtful that the Maple Leafs had any second thoughts about selecting him. He had 12 goals (third in the WHL) and 54 points (fifth) for Moose Jaw in 2012-13, then got some seasoning in the American Hockey League, playing 14 regular-season and five playoff games for the Maple Leafs' affiliate in Toronto.

Rielly also played for Canada at the 2013 IIHF World Junior Championship, where he had a goal and three points in six games.

He made his NHL debut Oct. 5, 2013, against the Ottawa Senators and became a regular right away with the Maple Leafs, playing 73 games in 2013-14. Among rookie defensemen he ranked second in the NHL in assists (25) and sixth in points (27).

Rielly got his first NHL point Oct. 10, 2013, with an assist against the Nashville Predators and scored his first NHL goal Dec. 16, 2013, against goalie Marc-Andre Fleury and the Pittsburgh Penguins.

He followed up that successful rookie season by leading Toronto defensemen in goals for the first time with eight in 2014-15 and getting his first multigoal game when he scored twice against the New York Rangers on Feb. 10, 2015.

Rielly played all 82 games for the first time in 2015-16, when he finished second on the Maple Leafs with 27 assists and tied for third with 36 points.

After finishing with 27 points (six goals, 21 assists) in 2016-17, Rielly had a breakout season in 2017-18, nearly doubling the previous season's total with 52 points (six goals, 46 assists). He took another big step the following season, scoring 20 goals and finishing with 72 points and a plus-24 rating, the first time he'd been a plus player in his NHL career.

Rielly's success continued in 2018-19, when he finished fifth in voting for the Norris Trophy as the best defenseman in the NHL with 72 points (20 goals, 52 assists) in 82 games. He signed an eight-year, $60 million contract (average annual value of $7.5 million) with the Maple Leafs on Oct. 29, 2021. The following season his overtime goal gave Toronto a 4-3 win against the Tampa Bay Lightning in Game 3 of the 2023 Eastern Conference First Round and his game-tying goal at 16:04 of the third period in Game 4 led to a 5-4 overtime victory. The Maple Leafs won the best-of-7 series in six games for their first postseason series win since 2004.

Rielly then became the first Maple Leafs defenseman with at least six assists in a playoff year since Brian Leetch had eight in 13 games in 2004.