Following his career with the
Western Hockey League's
Lethbridge Hurricanes, he was drafted in the third round, 48th overall by the
New York Islanders in the
1991 NHL entry draft. After multiple years playing for minor league affiliates in the
American,
International and
East Coast Hockey Leagues, McLennan was called up to the NHL and backed up veteran
Ron Hextall in the 1993–94 season. He was shaky with the Islanders however, winning only 17 games with a .889 Save% over three seasons. Struggling to find confidence, he spent his last two seasons in the organization alternating between the NHL club and the minor leagues. A few weeks after the
1995–96 NHL season had been completed, McLennan drove from
Salt Lake City, Utah to
Lethbridge, Alberta, on his way home to
Edmonton. While visiting family in Lethbridge he fell ill. He went to a hospital on May 6, 1996, after feeling sick all evening, with immobility setting in. What was thought to be the
flu turned out to be
bacterial meningitis. After nearly dying that day, he spent the following week in intensive care. The Islanders declined to renew his contract at the conclusion of the season. The
St. Louis Blues signed him to a contract that summer and he spent the following season in the minors. He returned to the NHL as the Blues' backup goalie for the
1997–98 NHL season. That year he was awarded the
Bill Masterton Memorial Trophy, awarded to the NHL player who best displays perseverance and dedication to hockey. In the 1999 off-season, the Blues acquired another backup goaltender,
Roman Turek from the
Dallas Stars, who easily won the Blues starting goaltender role. With the emergence of Turek and reduction of McLennan's games, the Blues won their first
President's Trophy in franchise history. Turek was subsequently awarded as the sole winner of the
William M. Jennings Trophy at season's end. That off-season, McLennan was left unprotected by the Blues in the
2000 NHL Expansion Draft and joined the
Minnesota Wild franchise. In his only season playing for the Wild, he set a career high in games played with 38, but finished with 32 losses and only 5 wins. Ultimately, he returned to the minors the following season. The
Calgary Flames acquired him in a trade for a pick in the last round at the
2002 NHL entry draft, where he again played the role of NHL backup goalie, but only won two games that year. Despite his timid performances, he remained with the team, once again as
Roman Turek's backup for the following season. When Turek became injured in the
2003–04 season, McLennan was thrust into the starting role. However the newly acquired
Miikka Kiprusoff soon took over as starter, reversed the team's fortunes, and led the Flames to their first playoff berth in eight years. Turek returned later thus making McLennan expendable. With the Flames looking to add extra toughness into the lineup for the upcoming playoffs, they traded McLennan away in a package deal to the
New York Rangers in March 2004. Seeking an astute goaltender to partner with highly touted rookie
Henrik Lundqvist, the Rangers signed free agent
Kevin Weekes to replace McLennan. He then signed a two-year contract with the
Florida Panthers, who were looking for a goalie that would only play sparingly with
Roberto Luongo. After the Panthers declined their contract option for McLennan the next season, he was brought back to Calgary in 2006 to backup
Miikka Kiprusoff. On April 21, 2007, McLennan entered a first-round playoff game versus the
Detroit Red Wings to provide relief to Kiprusoff. Immediately after entering the game, McLennan slashed
Johan Franzén twice in the leg. Losing his cool, McLennan asininely slashed Franzén a third time and in the stomach after play was stopped, earning a game misconduct, and forcing Kiprusoff to return to the net. The NHL suspended McLennan for five games and fined coach Jim Playfair $25,000 and the team $100,000 for their actions late in the game. After retiring, the backup goalie admitted he slashed Franzen believing he could spark a line brawl. As he never played in the NHL again, he remained under suspension after his retirement. That off-season, he signed with
Metallurg Magnitogorsk of the
Russian Super League but the team released him after 5 weeks due to poor performances and dislike from management and players. On November 21, 2007, McLennan signed with the
Nippon Paper Cranes of
Asia League Ice Hockey. McLennan announced his retirement at the end of the 2007–08 season. ==Coaching==