From the Pens Official Website

On Kris Letang playing the left side:
He’d be the other right-handed defender that’s going to play on the left side tonight. Someone has to go there if Brooks does not play. Kris has had the most experience and been the most comfortable there. It’s not a lot of experience, but it’s the most experience. He played there a little bit last year. He played there with Ben Lovejoylast year when Brooks was out at the end of the season, in a matchup situation a lot of times. So it’s not a ton of time, but he’s known here in training camp that’s a situation where he’d play on the left side a little bit. He’s practiced and gone through some reps. So it’s not a ton of experience, but Kris’ skating abilities allow him to probably be the best situation for us there.