Professional career
In 1973, Howe was approached with an offer for the upstart World Hockey Association with the Houston Aeros. Approached with a four-year offer worth $500,000 with a signing bonus of $125,000, Howe accepted the deal, which saw him paired up not only with his brother Marty but also his father Gordie, the latter of whom came out of retirement to play with his sons. Led by the Howes, the Aeros won the 1974 and 1975 Avco Cups, awarded to the league champions of the WHA. Mark, playing left wing, was awarded the Lou Kaplan Trophy as Rookie of the Year and earned 2nd team All-Star status. Having dual citizenship, he represented his father's country in the 1974 Summit Series, where he was one of Team Canada's leading scorers.
Even though Howe had played a complete season in the WHA, the Boston Bruins proceeded to select him anyway with their second-round pick in the 1974 NHL amateur draft. He was the first active WHA player to be drafted by an NHL team, and the first of three selected in the 1974 draft, the other two being his brother Marty, selected by the Montreal Canadiens in the third round, and Tom Edur of the Cleveland Crusaders, who was also selected by Boston. All three players opted to remain with their WHA teams after the draft.
With the 1976–77 season, Howe was utilized as a defenceman by head coach Bill Dineen for select games due to a litany of injuries suffered by the Aeros. Before the 1977–78 season, the Howes moved their family act to Hartford, Connecticut to play for the New England Whalers.
When the NHL and WHA merged in 1979, one of the four WHA teams left standing were the Whalers, who changed their name to the Hartford Whalers. In the 1979 NHL Expansion Draft, the Boston Bruins, who held his NHL rights, attempted to reclaim Mark Howe; however, the Whalers used a priority selection to retain him. Due to a gentlemen's agreement between the Whalers and the Red Wings, Detroit opted not to exercise their right to reclaim Gordie Howe; the Wings also opted not to reclaim Marty, whose rights they had previously acquired from Montreal. As a result, Mark, his father and his brother were able to play one more season together with the Whalers, this time in the NHL. During that season, Howe was moved over to the defenseman position for the first time in the NHL prior to a December game against the Buffalo Sabres. He ended up with 80 points in 71 games while finishing fifth place in Norris Trophy voting. Howe played the left wing position for the 1980–81 season, which proved to be one of Howe's best. Howe was a mid-season All-Star, and in the fall, he appeared for the US national team at the 1981 Canada Cup tournament. It was his last as a full-time left winger before moving to defenceman on a permanent basis.
Howe was involved in one of the more memorable injuries in NHL history. On December 27, 1980, he slid into the pointed metal center of the net and cut a five-inch gash in his rectal area. He was essentially impaled in an injury that nearly ended his career. Following a lawsuit by Howe, the NHL changed the design of its nets so that there would no longer be a center portion that jutted up toward the goal line. He lost 21 pounds and his stamina suffered after requiring a liquid diet to avoid intestinal infections. After Whalers management lost faith in Howe, he requested a trade, and was moved in a four-player deal that also involved draft picks, to the Philadelphia Flyers.
The backbone of one of the NHL's best defensive teams of the mid-1980s, Howe was a finalist for the Norris Trophy three times, those being in 1982–83, 1985–86 and 1986–87 season. Howe credited the advice of former Flyers player Ed Van Impe (who advised him to play within the system along with being aware of opposing forwards and trusting teammates) and also being able to watch the games on television (at the time, Philadelphia had more games on television than Hartford, albeit late at night). His Philadelphia team, backstopped by Vezina Trophy-winning goaltender Pelle Lindbergh, finished the 1984–85 season with most points and earned a berth in the Stanley Cup Final, only to lose to the Edmonton Oilers' dynasty, which featured stars such as Wayne Gretzky, Paul Coffey and Mark Messier.
Howe had his best season during the 1985–86 season where he posted some of the best numbers ever by an NHL defenseman, in particular, leading the NHL with a remarkable +85 Plus/Minus rating and 7 shorthanded goals. He scored 24 goals, added 58 assists for 82 total points while being the lifeline out of the Flyers defensive zone with his outstanding skating and passing abilities. Unfortunately for Howe, Paul Coffey had perhaps one of the best seasons by a defenseman in NHL history, breaking Bobby Orr's single-season records for goals with 48, and tallying 138 points. Howe, for the second time, finished runner-up in Norris Trophy voting.
The 1986–87 season brought great success to both Howe and his Philadelphia Flyers teammates. The Flyers, for the third consecutive season, led the Prince of Wales Conference in points. Led by Howe and defense partner Brad McCrimmon, rookie netminder Ron Hextall, and a line featuring Brian Propp, Rick Tocchet and Pelle Eklund, the injury-riddled Flyers took the vaunted Edmonton Oilers to 7 games in the NHL Finals before succumbing 3–1 in the finale.
From 1979 to 1988 for the position of defenceman, Howe was third in points and plus-minus.
After the 1991–92 season, the Flyers granted Howe free agency. Seeking to play for a contender to win the Cup, Howe had four teams in mind: the Pittsburgh Penguins, New York Rangers, New Jersey Devils and the Detroit Red Wings. Pittsburgh (who he labeled as wanting to play for the most) did not return his call so he shifted his interest with the "next choice" with Detroit that had appeal to him with the talent present. The 1994–95 season saw him play in eighteen games for six total points as the Red Wings appeared in the Stanley Cup Final, which they lost to the New Jersey Devils in four games.
