Tuukka Rask vs. Frederik Andersen

Goaltending is an integral part of the Stanley Cup Playoffs. To better understand the strengths and weaknesses of each goaltender, the last 100 goals allowed for each goaltender were charted, with the help of Double Blue Sport Analytics from Upper Hand Inc., to see what patterns emerge.

RELATED: [Complete Bruins vs. Maple Leafs series coverage]
Toronto Maple Leafs starter Frederik Andersen and his Boston Bruins counterpart Tuukka Rask each had their share of ups and downs this season, including some late-season struggles. Now they meet in the Eastern Conference First Round, which starts Thursday with Game 1 at TD Garden (7 p.m. ET, CBC, TVAS, NBCSN, NESN). Here is an in-depth look at each goalie's game:

Tuukka Rask, Boston Bruins

It's been a roller-coaster season for Rask, who lost his starting job early in the season, regained his 2014 Vezina Trophy form in mid-February, then sagged late. Some of that is expected with a flow-based style that relies a little more on skill and timing, but with a .928 career playoff save percentage that is tied for sixth, with Matt Murray of the Pittsburgh Penguins, among goalies with at least 30 playoff appearances, bet on him to be ready for Toronto's dynamic attack.

Goal trends

Early butterfly: If there was one thing that jumped out amid Rask's recent struggles, it was how early he was dropping to the butterfly; not in terms of dropping early on shots, but more cases of him sliding across the crease on his knees on plays we'd normally expect him to handle on his skates. He wasn't getting a lot of help defensively, however. Of the 100 goals tracked, 50 came after a pass or play across the slot line, an imaginary line that splits the offensive zone from the goal line to the top of the face-off circles. That's well above the 33.9 percent average of tracked goals while breaking down playoff goalies for this project during the past two seasons. These plays are hardest for goalies because it forces them change their angle from one side to the other before a quick shot. Twenty-one of 50 "slot line" goals against Rask came after Feb. 15. Add in another 21 goals on lateral plays that did not cross the slot line but at least forced Rask to change his angle and its clear forcing him to move is key to scoring.
Low and wide: Last season, Rask gave up 26 percent of his goals along the ice outside of his skates; this season it was 28 percent, with the biggest number of those going in low to his right. It's often an indication of a back-door play and, certainly, the number of slot-line chances he faced played a role in many of those goals. But the way Rask plays these rushes, often starting outside his posts laterally before the initial pass also makes it harder for him to recover that space on quick shots, which accounted for 44 percent of his goals this season.
Post play: Rask continued to modernize his post-integration habits during the season, using his back leg more to pivot around and move off his posts from reverse-VH. He eliminated some of the inherent exposure from his old tendency to go into the posts with the shin of his pad and "bump" off them with a narrow butterfly that limited his coverage along the ice. It showed with only 12 goals on low-high and sharp-angle plays, compared to 21 last season.
Notable numbers: Rask's numbers mid-to-high on the glove and blocker sides were at, or lower than, average; but he allowed several goals on clean shots off the rush. His pattern of drifting back in straight lines, not staying square to shooters down the wing, was a factor. It shows up more on his blocker side with 10 percent of goals from outside the home plate area.

Frederik Andersen, Toronto Maple Leafs

No NHL goaltender faced more shots this season than Andersen, who stopped 91.8 percent of 2,211 shots. It's hard to imagine a degree of difficulty as high on most occasions for other goalies, either. Despite another slow start, some late-season struggles and facing quality scoring chances throughout the season, Andersen finished with a franchise-record 38 wins while continuing to build on a well-balanced approach that lets him use his 6-foot-4 frame efficiently, without sacrificing too much of his reactionary game.

Goal trends

Move him to the blocker: Every goalie has a dominant side, one they feel more comfortable moving toward. For most, including Andersen, it's the glove side. Despite that comfort level, most goalies still give up more goals above the pad on the glove side. Andersen's totals are higher above the blocker-side pad, however. His movement to his blocker side can be flat and off angle, forcing him to get set and square after he arrives, rather than building those elements with early rotation before he moves. He does this better going in the opposite direction. The increased number of goals allowed from outside the home-plate area on his right is another example.
Low-high attacks: Andersen has a nice mix of post-integration options on sharp-angle attacks and, for a second straight season, he had only one charted goal came from below the goal line. But the number of goals from low-high plays was also higher than the 18.3 percent average, with 29 of the 100 goals on passes originating from near or below the goal line. Nineteen of those goals were finished off by one-timers, which doesn't give a goalie time to push off the goal line and gain depth. Andersen also tends to lean past his post and lose his back-skate engagement in reverse-VH, which delays his ability to get back into the middle of the net.
Notable numbers: Consistent with the higher quality of shots Andersen faced, 72 of the 100 goals tracked contained a lateral element in the shot build up, and 41 percent featured plays across the slot line. Add in 51 one-timer or quick-shot goals, and that's a lot of pressure on the goalie to quickly beat a play side-to-side and get set. Andersen was only beaten clean on 17 shots where he had time to get set and see the release, but gave up 24 goals on rebounds, with the degree of difficulty on the first shot often a factor.