By Michael Hurley, CBS Boston

BOSTON (CBS) — The Blues by and large outplayed the Bruins on Monday night in Game 4, but the Bruins still could have won the game to take a 3-1 series lead and welcome the Stanley Cup to the TD Garden on Thursday night.

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Ultimately, though, the Blues just applied too much pressure for Boston on this net, leading to a couple of breakdowns at critical moments. The Blues capitalized, and as a result, it’s a whole new series.

The first defensive miscue came late in the first period, with the score tied at 1-1. Brayden Schenn held a puck along the wall, alone in the offensive zone against four Bruins skaters. Schenn looked up and sent a pass from the left faceoff circle back to the right point, with the puck getting past Connor Clifton thanks to a stick lift from Jaden Schwartz.

The puck ended up on the stick of Alex Pietrangelo, at which point Vladimir Tarasenko coasted directly down the slot, perhaps unobserved but certainly unobstructed by the Bruins on the ice.

Pietrangelo craftily dragged the puck to remove Marcus Johansson from the shooting lane before firing a shot on net. Tuukka Rask stopped Pietrangelo’s shot with a kick save, but the puck rebounded directly in front to Tarasenko. With no Bruins around to even get a stick near him, Tarasenko easily scored on the rebound to regain a lead for the home team.

The Bruins were back and had numbers, but in a matter of just three seconds, they went from completely comfortable to seeing the puck in their net.

Clifton was in position to prevent that opportunity for Schwartz, while Zdeno Chara was focused on keeping Schenn away from the net. That left center Charlie Coyle or winger Danton Heinen to take care of Tarasenko, but neither player was in Tarasenko’s zip code.

An overhead view of Tarasenko just after releasing the shot shows just how much room the forward had to operate.

Vladimir Tarasenko scores in Game 4. (Photo by Jamie Squire/Getty Images)

The same issue would rear its head for Boston on what turned out to be St. Louis’ game-winning goal.

The Bruins made a line change midway through the third period but once again had numbers in their own zone, with four skaters to St. Louis’ three. So, absent much of an opportunity on a rush, Pietrangelo teed up a blast from about 50 feet.

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Rask made the save, but the rising slapper was difficult for the goaltender to contain, leading to a rebound in front of the net. The Bruins should have had at least one body in position to prevent a Grade A scoring opportunity for a streaking Ryan O’Reilly. Alas, nobody picked him up.

O’Reilly made a skilled play to swat the puck out of mid-air to score the goal, but nevertheless, a Bruins skater should have been able to prevent him from getting such a clean shot from the goalmouth.

Heinen had turned his back to O’Reilly to lose sight of him, and Charlie McAvoy’s stick check did nothing to interfere with O’Reilly’s opportunity to put his own stick on the puck.

The still photos tell the story pretty well:

Ryan O’Reilly scores the game-winning goal of Game 4 of the Stanley Cup Final. (Photo by Jamie Squire/Getty Images)

Ryan O’Reilly scores the game-winning goal of Game 4 of the Stanley Cup Final. (Photo by Bruce Bennett/Getty Images)

Ryan O’Reilly scores the game-winning goal of Game 4 of the Stanley Cup Final. (Photo by Jamie Squire/Getty Images)

Given that O’Reilly’s tally would end up being the game-winner, the spotlight on that breakdown grew brighter.

Rask’s inability to swallow both Pietrangelo shots surely contributed to the goals, but it would have been a non-issue if the Bruins had just been able to keep a body on the Blues as they burst to the front of the net.

Rask had been nearly unbeatable all postseason long, and in terms of getting beaten on clean shots, he still may be. But clearly, the Blues figured the best way to beat him would be on goals exactly like these two. It worked to perfection in Game 4, and it will give the Bruins an obvious area of focus for Game 5.

The Blues managed to generate 64 shot attempts, 23 more than Boston. Thirty-eight of those shots made it on net, compared to Boston’s 23. By that measure, the Blues deserved this victory. With some timely scoring and good goaltending, though, the Bruins had a chance to prove that “deserve” doesn’t have to mean a thing.

Those two goals are sure to be viewed differently by both sides. The Blues have to feel rewarded by putting forth more effort and executing in those brief spurts. The Bruins have to feel like they let an opportunity slip by.

Both sides are correct, but from the Boston side, those back-breaking goals have to feel like unforced errors. As a result, the dynamic of the entire series has shifted.

The Bruins could have stolen Game 4. Really, they should have stolen Game 4. Two quick breakdowns — and two heads-up plays by the Blues — ensured that would not happen.

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You can email Michael Hurley or find him on Twitter @michaelFhurley.