With injured Ryan McDonagh and Dan Girardi not expected to play in Tuesday’s Game 3 — and perhaps not in Thursday’s Game 4 — of the best-of-seven series against the Penguins at Madison Square Garden, the Rangers are supplementing their defense, and perhaps their power play.

Raphael Diaz, the 30-year-old Swiss veteran who played 15 games with the team in 2013-14, and 37 in Hartford this season, will practice with the club Monday. At the very least, Diaz will give coach Alain Vigneault and his staff a healthy seventh blueliner who has played for four NHL teams and has 125 regular-season and 12 playoff games under his belt.

With the series tied 1-1, whether Diaz dresses for Game 3 is unclear, but the choice appears to be between him and Dylan McIlrath on the third pair. Both are righties, and Vigneault said, “those are decisions we’re going to make on a game-to-game basis.”

McIlrath played just over nine minutes in Game 2, but less than five minutes in the second and third periods, and fellow rookie Brady Skjei, a lefty, was used a little on the right side. Diaz has played the left side, Vigneault said, “but like most of our ‘D’ are more comfortable on his natural side.”

Each brings different qualities to the rink: McIlrath is a stronger and more physical player, with a hard shot. Diaz is a better skater and is experienced at playing the point on the power play.

“We like to play fast, and as much as we can, make clean plays out from our end,” Vigneault said. “Pittsburgh is doing a lot of the same things, we’re trying to slow them down as best as we can.”

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What does having Diaz mean for Girardi, a warrior who is now 31 and also a righty, who has struggled with knee and ankle issues this season? Another decision for Vigneault, who supported Girardi in a conference call with writers Sunday.

“When he is healthy, Dan, in my estimation, is a real solid defenseman, he plays through more things than I’ve seen a lot of players I’ve coached play through,” Vigneault said. “He’s always team-first, and it’s always ‘I can play’, and sometimes the medical staff and the coaching staff say, ‘Well with this here, it’s probably better if we give you a little more time to get better.’ If it was up to Dan, he’d be playing. I think he’s probably been unfairly criticized and when he’s ready to come back, I’m sure he’s going to play real well for us. He’s given us some real good games this year, he’s given us some great years since I’ve been here, he’s one of our best competitors and a guy who’s really respected in our dressing room because of who he is and what he can bring.”

Notes & quotes: Game 3s of series haven’t been particularly kind to the Rangers in the past three springs. Last year, they won in Pittsburgh, but lost in Washington and Tampa. In 2014, they beat the Flyers on the road, but lost to the Penguins, Canadiens and Kings at home. In 2013, they won in Washington, but lost at home to the Bruins . . . On the flight home from Pittsburgh, Vigneault and general manager Jeff Gorton compiled a list of Hartford players to be summoned as part of a taxi squad. They will undergo medicals and exit meetings Monday, and will report Tuesday or Wednesday.