Forward David Pastrnak was in the Bruins’ lineup for the first time this season on Saturday night at Washington. Nick Wass/Associated Press

The Boston Bruins’ power play has seen its share of significant changes and disruptions this year.

Until Saturday night in Washington, the top unit had been missing it’s most gifted scorer, David Pastrnak. Defenseman Matt Grzelcyk, the replacement for the departed Torey Krug on the power-play unit, has been in and out of the lineup.

And yet the Bruins’ power play, so good the last few seasons, has not missed a beat. The Bruins went into Saturday’s game clicking at 35.4 percent, fourth-best in the league.

Depth in personnel, good puck movement and simplification have been the keys, said Patrice Bergeron.

“Any time you’re missing those guys and there are guys like (Charlie) McAvoy and (David) Krejci coming in, or (Nick) Ritchie, who’s been awesome as well, it makes things easy,” said Bergeron, who has three power-play goals. “I think we’ve been watching a lot of videos, talking, communicating as well. But also, we move the puck fast and not force plays, and I feel like we’ve put the puck on net early in power plays and it’s been helping a lot, just to get the (penalty killers) moving and thinking a little bit more and keep them on their heels. (It’s helping) to generate chances off the rebounds and retrieving pucks and working hard to get it back.”

Pastrnak made his season debut Saturday night, which presented Coach Bruce Cassidy with a delightful dilemma. He was able to insert one of the league’s best goal scorers onto the top unit, but who should get moved out? He toyed with playing five forwards, but that could present some problems if the group got into a defending situation. Instead, the plan Cassidy chose, at least to start, was the most simple one, moving Krejci to the second unit to make room for Pastrnak.

Also, Cassidy held firm on the biggest wrinkle – literally and figuratively – to the power play this year, keeping Ritchie as the net-front presence.

“I like him net front so we’ll keep him there,” said Cassidy. “The adjustment we could make is put (Brad) Marchand back to the net front, move Krech to the elbow and have Charlie McAvoy up top and put Ritchie on the second unit. But I think (Ritchie) has earned the right to stay there. He’s a little different flavor. He’s been an option for us when they’ve taken away Bergeron from the bumper. He’s good at recovering pucks, he’s a tough guy to move and presents his stick well for those back door tap-ins.”

After the Bruins went down 3-0 on Saturday, Cassidy did go with a five-forward unit and it paid off when Krejci’s slapper went off a Washington stick and bounced off Ritchie, who was credited with his fourth goal of the year late in the second period. Boston finished 1 for 4 on the power play.

GRZELCYK MISSED HIS third game of the season on Saturday because of a lower body injury, which opened up more playing time for Connor Clifton. Given the vital role Grzelcyk is expected to play for this team, the bumps he’s taken have to be concerning for Bruins’ management. Just how well Clifton, a right shot, can fill in for Grzelcyk on the left side could very well color the front office’s thinking on whether they need to acquire another left-shot defenseman.

Cassidy had brought up the idea of Clifton playing on the left side in training camp, and it didn’t take long for that Plan B to become necessary while John Moore has been unavailable because of a lower body injury.

“It’s obviously a little different. But playing with (Brandon Carlo), we complement each other well. But I think back a couple of years ago, Kevan Miller used to play the left side as a righty. I definitely saw some clips early in the year,” said Clifton.

“Early on, (Cassidy) discussed with me that I might get in on the left side after (Zdeno Chara) and Torey both leaving, both playing huge minutes, so that was a factor early on, though I didn’t get too many reps on the left side really until after that first game. But I thought it’s been going well.”

Clifton admitted to being tentative his first game on the left side, but felt his second game went much better. He said the biggest adjustment is at the point in the offensive zone.

“D-zone, it’s fine. Really, the only time you notice it is O-zone blue (line), especially when it’s a rim-out,” said Clifton. “Obviously if it’s a rim out to my side, I’ve got to handle it on my backhand and hopefully pull it to the middle and make a play. It definitely takes an extra half second or so. But it is what it is, and I think it’s been going well so far.”

With Jack Studnicka banged up, Karson Kuhlman, who missed most of training camp because of COVID-19 testing issues, also made his season debut on Saturday night.