PHILADELPHIA — Travis Hamonic needed a maintenance day off from Friday’s practice but that turned into missing Saturday’s game here with a lower-body injury.

Hamonic took a shot off his right heel during Thursday’s 4-1 loss to the Capitals and then finished that game by taking a high, hard hit from Alex Ovechkin. Hamonic had played all 41 games this season.

With Johnny Boychuk already out another month, the Isles were down their top two right-handed defensemen.

Scott Mayfield, summoned from Bridgeport on Friday, made his season debut on Saturday afternoon against the Flyers, paired with Adam Pelech, his regular defense partner with the Sound Tigers this season.

“I think they handled themselves pretty well,” Jack Capuano said of the two rookies.

Nick Leddy played the right side with Calvin de Haan and Brian Strait jumped into the lineup in place of Marek Zidlicky to pair with Thomas Hickey. Isles defensemen had seven of the team’s 20 shots on goal, with Hickey’s three leading the way.

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Hamonic is officially day to day. The Islanders next play Tuesday at Barclays Center against the Blue Jackets.

Power play continues to sink

Capuano said on Friday he was starting to be encouraged by the team’s power play, which went 2-for-7 against the Stars on Sunday then produced nine shots in two failed chances against the Caps on Thursday.

It may be back to the drawing board after Saturday, with the Isles mustering only three shots in 3:31 of power play time, and all of those were on their first power play early in the second period.

Twice the Isles cut their own advantages short by taking penalties. Mikhail Grabovski crashed into Flyers goaltender Steve Mason to end one power play and Anders Lee was whistled for tripping off the faceoff at the start of another.

The penalty kill was the lone bright spot, going 5-for-5 to improve to 86.4 percent efficiency, second in the league.