The thesis on Duncan Keith was that he was a product of the new NHL after the Great Bettman Lockout II. The thought was that he wouldn't have survived in the clutch and hogtie era because he was so small. It isn't necessarily true, as anyone with the instincts of the man could have played at any time, and he was certainly no peach to forwards in the corner or in front of his own net. Even if he didn't incapacitate as many, he was still nice to play against.
The removal of the red-line and the two-line pass was one of the rules changes that made the game more open. It was a group of contradictions. He wasn't all that skilled with the puck, but he put up a lot of points. He was one of the fastest skaters in the league, but he was also one of the more awkward and choppy looking skaters. The best work was done before the opposing forward entered the defensive zone.
Since the red line was gone, more and more teams have decided to go through the neutral zone instead of dumping the puck in. The game sped up as stretch passes over half the ice became commonplace. When teams were able to gum up the neutral zone through puck traps and holding, forwards were sitting ducks for any defense and couldn't generate much speed to get to the ball. They tried to force turnovers and conceded that they had to trap. Without a red line, those races to the puck behind the goal line were a viable way of attacking.
The Hawks rose to prominence because they made sure those races never happened. The teams could try and dump the puck in front of him, but he was too quick to get there. In order to have the foresight to jump up ahead of his line, cut off the play before that dump-in or play at the blue line, or that forward could receive a pass, he needed to have that knowledge. Wingers and centers were forced to make decisions quickly because he shrunk the ice. He was able to do that because of his recovery speed. He was helped by the Hawks forwards, who were dedicated to backchecking. They pushed opposing puck- carriers into the rocks. The prototypical play was for Keith to force a turnover just outside his blue line, poking the puck ahead to start a rush, and then assisting on a second goal. Eddie Olczyk got a second Norris trophy by harping on the secondary assists on every national broadcast he could. Most of his points were accrued in this way.
He averaged 31 minutes a night in the playoffs in 2015, when the Hawks were reduced to using only four d-men due to the injury of KimmoTimonen. In 23 games, he scored 21 points, including the Cup-winner in the Final. His trophy case was filled with more than one trinket, including two gold medals and three rings.
Teams gave up trying to get into the Hawks zone on the other side of the ball when it came to star corners. It came down to getting pastBrent Seabrook on the other side, which meant some degree of physical punishment for whoever chose that task. It was a great compliment.
Nicklas Lidstrom played a game that squeezed off space without anyone realizing it until he stripped the puck. The more frantic of the two was trying to end things quickly. The first engagement usually won possession with opposing forwards caught up the ice.
Most of the teams in the NHL tried to defend that way. It is now possible for the best d-men in the league to carry the puck out of their zone on their own.
Hockey moves too fast and is cut down too quickly. It was obvious to see how small the ice was when you watched the Hawks. He wasn't a threat for a big hit, but he could become crazy. He would always turn the play around with them unprepared for the Hawks forwards because they didn't fear for their safety as much.
When the other team stops trying you, it's the biggest compliment you can get.