Thursday night’s matchup of the Capitals’ Alex Ovechkin and the Oilers’ Connor McDavid ended in Edmonton’s favor. (Perry Nelson/USA Today Sports)

Washington Capitals Coach Todd Reirden expected his penalty killers to go through growing pains early in the season. Given new concepts and different personnel, Reirden knew it would take some time for the group to get up to speed.

In his first year as the team’s head coach, Reirden targeted the penalty kill as an area in which he wanted to divert from Barry Trotz’s style. This season — not unexpectedly, given all of that — the Capitals’ penalty killers have struggled.

After allowing a power-play goal in the first period during a 4-1 loss to the Edmonton Oilers on Thursday night at Rogers Place, the Capitals have allowed at least one in each of their past six games. Washington also allowed a shorthanded goal in the second period.

“We are coming up on Game 10 here, and it is definitely a work in progress in that department,” Reirden said of the penalty kill. “We can be better for sure in that regard.”

Under Trotz, the unit relied on center Jay Beagle, a faceoff ace who signed with the Vancouver Canucks in the offseason. And the Capitals also are without hard-hitting forward Tom Wilson, in the midst of his 20-game suspension after an illegal check to the head of St. Louis Blues forward Oskar Sundqvist in the preseason. NHL Commissioner Gary Bettman ruled Thursday to uphold Wilson’s ban.

The Oilers, who finished 1 for 4 with the man advantage, scored their first goal 16:28 into the first period when defenseman Evan Bouchard found the net from the point. It was the 19-year-old’s first NHL goal; he became the youngest defenseman in Oilers history to score. Blocking Capitals goaltender Braden Holtby’s view in front of the net was ex-Capitals forward Alex Chiasson.

“I was looking far right, just to see his stick blade, and I kind of saw the release go on that side, but I didn’t really have a clue where,” Holtby said. “There were quite a few guys [in the way] and, again, I have to see if there is a better view that I could have got to, so I could have seen exactly where it was going to go.”

The Capitals’ penalty kill, which came into the game ranked 25th in the NHL at 71.9 percent, almost killed off that power play; Bouchard scored with three seconds left on Michal Kempny’s tripping penalty.

“I thought we were able to create some momentum and make it difficult,” Reirden said. “They have a good power play and some dangerous players. . . . They get one at the end of the power-play opportunity at the end of the first period, and the rest of the way we did a pretty decent job of disrupting and taking away some time and space from there and getting up ice and getting some offense the other way.”

Chiasson, a member of the Capitals during their Stanley Cup run last year, joined the Oilers on a one-year contract. He showed his ex-teammates what they’re missing when he scored with 10:44 left in the third period; the goal gave the Oilers a 3-1 lead, and it was Chiasson’s third goal in his past two games.

The Capitals couldn’t convert on their lone power-play opportunity — but the Oilers did. Edmonton took a 2-0 lead at 10:06 of the second period on a shorthanded goal by forward Ryan Nugent-Hopkins. Capitals defenseman John Carlson turned the puck over at the Washington line, and Nugent-Hopkins slipped the puck past Holtby.

“Just a bad play, really,” Carlson said. “I had plenty of other options to do and just made a bad play.”

Holtby kept Washington in the game all night, making eight saves in the first period and 13 in the second period. He made three point-blank saves on Oilers star Connor McDavid, who later scored an empty-netter with 1:17 left. The loss dropped the Capitals to 1-1 on their annual visit to western Canada, which wraps up Saturday afternoon in Calgary.

Fourth-line forward Andre Burakovsky scored the Capitals’ goal 12:21 into the second period to cut the Oilers’ lead to 2-1. It was Burakovsky’s first point of the season. Center Nic Dowd was credited with the primary assist — his first point since a goal in the Capitals’ opening night win against the Boston Bruins on Oct. 3.

Burakovsky was dropped to the fourth line alongside Dowd and newcomer Dmitrij Jaskin last week.

“I felt like his game was coming,” Reirden said. “I thought in Vancouver [in a 5-2 win Monday] he did some really good things, and [we] tried to slot him up with different guys just because I thought he was really going tonight. Could have had a couple other goals as well, but he has made some good plays.”