Selected by the San Jose Sharks in the second round (No. 35) in the 2005 NHL Draft, the man affectionately known as Pickles was an instant hit, and he became a regular in the Sharks lineup at age 19 in the 2006-07 season.

The 6-foot-1, 205-pound defenseman led NHL rookies in ice time (22:12) and was third on the Sharks. Vlasic was named to the NHL All-Rookie Team along with teammate Matt Carle, the first defensemen from the same team to sweep the all-rookie spots since Nicklas Lidstrom and Vladimir Konstantinov of the Detroit Red Wings in 1991-92. With his patient game, efficient puck-moving skills and ability to take away the puck without resorting to physical play, Vlasic's game is often compared to that of Lidstrom, a seven-time Norris Trophy winner.

Vlasic's durability is also impressive; he played 253 consecutive games from Jan. 15, 2007 through Jan. 28, 2010.

He tied for the team lead with a plus-21 rating in 2009-10 and led the Sharks in blocked shots in 2010-11 with 147. He was again tops on San Jose with 171 blocked shots in 2011-12, and had eight blocks Dec. 23, 2011, against the Los Angeles Kings.

On March 20, 2013, against the Edmonton Oilers, Vlasic became the fourth Sharks defenseman to play 500 games, following Mike Rathje, Marcus Ragnarsson and Scott Hannan.

Following a solid 2013-14 season, in which he tied for ninth in the NHL with a plus-31 rating, Vlasic received votes for both the Norris and Lady Byng trophies. He was also a key player as the Sharks reached their first Stanley Cup Final in 2016.

Before his NHL career, Vlasic won the Memorial Cup with Quebec of the Quebec Major Junior Hockey League in 2005-06, and in three seasons there scored 22 goals and 113 points and had a plus-minus rating of 86. On March 20, 2016, Quebec retired Vlasic's No. 44 jersey.