2010-11: Brett Lernout played for the Warriors in the Winnipeg City Midget League. In 31 games he scored 3 goals with 12 assists and had 67 penalty minutes.
2011-12: Lernout attended the Saskatoon Blades pre-season camp and later appeared in two WHL games with the Blades a 16-year-old. He skated briefly for the Steinbach Pistons in the junior A Manitoba Junior Hockey League and was one of the top defensemen for the midget AAA Winnipeg Wild. Lernout was -2 with no points nor penalties skating for the Blades. He had one assist in six games with Steinbach. In 53 games for the Winnipeg Wild (including nine games in the MMHL playoffs), he scored 9 goals with 21 assists and 78 penalty minutes. Winnipeg won 41 of 44 games in the regular season and were unbeaten in the MMHL playoffs but lost to the Western Division champion Southwest Cougars in the 2012 Telus Cup West Regional.
2012-13: Lernout began the year with Saskatoon and skated in 18 games for the Blades before being acquired by Swift Current in a December trade. In 59 games between the two teams he scored 1 goal with 1 assist and was -4 with 28 penalty minutes as a WHL rookie. Swift Current finished third in the East Division and lost to Calgary in a first round playoff series. Lernout was -2 with no points nor penalties in five playoff games.
2013-14: Lernout skated in all 72 regular season games for Swift Current and led the Broncos with 103 penalty minutes in his second WHL season. He scored 8 goals with 14 assists and was +7. The Broncos finished second in the East Division and lost to Medicine Hat in six games in a best-of-seven playoff series. Lernout had 1 assist and was -1 in six playoff games. He was ranked 52nd amongst North American skaters in the Central Scouting final rankings and was selected by Montreal in the third round (73rd overall) in the 2014 NHL Draft.
2014-15: Lernout signed a three-year entry-level contract with Montreal in December 2014; making his pro hockey debut in April with Canadiens’ AHL affiliate Hamilton following his junior season with Swift Current. Lernout was -1 with no points and 2 penalty minutes in six games with Hamilton. The Bulldogs finished third in the North Division, six points behind the Chicago Wolves for the final Western Conference playoff spot. Lernout scored 14 goals with 28 assists (both career highs) in 72 regular season games for Swift Current and was -12 with 68 penalty minutes. The Broncos made the playoffs after finishing third in the East Division. Lernout scored 1 goal and was -7 with 4 penalty minutes in four playoff games as Swift Current was swept by Regina in a first-round series.
2015-16: Lernout made his NHL debut with the Canadiens in an April 2nd game against Florida after skating for the AHL’s St. John’s IceCaps in his first pro season. He had no points nor penalties in 6:30 minutes of an ice time with Montreal, suffering a knee injury that kept him out of the final three games of the season. Lernout scored 2 goals with 10 assists and was -4 with 73 penalty minutes in 69 regular season games with the IceCaps. St. John’s missed the AHL playoffs, finishing fifth in the North Division.
Lernout is a large, mean and nasty blue-liner. There are not too many of his nature currently in the Canadiens pool of prospects. He strives at making the lives of opposing players miserable, using his imposing size to clear the crease and battle in corners and behind the net, often winning the hunt for loose pucks. His defensive awareness is above average, but other areas could use some progression. He has a heavy slap shot, but has not managed to put all the tools together yet in order to take full advantge of that trait. His skating is good for his stature and he covers large portions of the ice with good footwork and a strong pivot.
Lernout skated for Montreal AHL affiliate St. John's in 2015-16 in his first pro season, making a cameo appearance in a late season game with the Canadiens before suffering a knee injury. A hard scrabble throwback defender who plays a punishing game, Lernout projects as an effective second or third pairing shutdown defenseman.