PITTSBURGH — So is this how Dan Boyle’s terrific career comes to an end: in street clothes, watching from the press box?

The 39-year-old defenseman was a healthy scratch for the Rangers’ season-ending 6-3 loss to the Penguins on Saturday afternoon at Consol Energy Center. Boyle has played out the two-year, $9 million deal he signed with the Blueshirts in the summer of 2014, and he has been open about his thoughts of retirement.

Though his tenure with the Rangers was a disappointment, this is an inglorious way to bow out.

“It was a very tough decision that took a lot of time to think through,” coach Alain Vigneault said. “It wasn’t easy to make. He’s been there for the team the whole year. But at the end of the day, you’re in this to win and I had to go with what I thought was the best lineup.”

Vigneault did get two righties into the lineup, with Dan Girardi returning from his three-game injury absence and Raphael Diaz going into his first NHL action all season in hopes of helping the dormant power play. Even with seven defensemen dressing, Boyle was on the outside looking in.

“I thought that [Girardi] would come in and help the [penalty kill], and Diaz would come in and I wanted a shooter on the power play up top,” Vigneault said. “That’s how I came to those conclusions. Somebody had to come out, and it was Dan.”

Boyle was seemingly ill-fitted for Vigneault’s Rangers since Day 1. Even well into his second season, Boyle spoke about assimilating to the new system, and how it was difficult to play a lesser role with lesser ice time than he had during his prime years with the Lightning and Sharks.

Boyle was brought in with the hopes of helping the power play, yet he was on for just one 5-on-4 goal since Christmas. That covered a span of 87:39 of man-advantage time in the regular season, plus another 11:36 through the first four games of this series, when the Rangers had gone 1-for-15 on the power play, the one goal coming 5-on-3.

The struggle continued with play in his own zone, as Boyle often got beat on the boards and in front of the net. Having been so used to skating the puck out of the zone when he was younger — and such a better skater — Boyle never could quite find the rhythm of that first quick pass that Vigneault demands of his defensemen.

His inability to fill those roles forced the hand of general manager Jeff Gorton to go out and get someone who could, trading a costly bundle to the Coyotes in exchange Keith Yandle at last year’s trade deadline.

Now Boyle’s tenure as a Ranger is over, and it leaves a sour taste in the mouth of Rangers fans. While wearing the sweater, he was so different than that offensive powerhouse lifting the Stanley Cup with Tampa Bay in 2004, or that elusive, swift-skating quarterback with San Jose. He was a big-time disappointment for the Blueshirts, and that might be how his career ends — watching instead of playing.

“It was a very tough decision,” Vigneault said, “that took a lot of time to think through.”