I think - and maybe I'm naive here - that the NHL is honorable in that teams really would prefer to win against the best version of the other team.
It's possible the Capitals are happy to face a Penguins team down Letang, Crosby, Murray and Sheary. It sure gives them a better chance to win.
But it also ratchets up the pressure to a maximum (relative to this being entertainment, obviously).
The Caps were expected to beat the Penguins at the start of the series. Partly because they're the three-time Regular Season Champs with a rep for failing in the Playoffs (undeserved). Party because their arch rival wasn't facing them with their best lineup.
The Penguins are lucky not to be down 3-0 with the way they've played, so the Capitals have to put the pressure aside, forget about how things should be, and keep playing the way they have been.
With Letang and Murray out you weren't facing anything close to a full-strength Penguins lineup. Now with Crosby and Sheary also you you're facing a decrepit shadow of the Penguins.
And they can still win - Playoff hockey being what it is, that 2-1 advantage is huge. Injuries or not, you're still playing a good team with tons of talent. And they're winning.
So the Capitals can't be assured of anything, but for a team that has been achingly unlucky in the last couple Playoff seasons, it is a huge break.
No one wants to see Crosby take any more hits to the head - the game is bigger than anyone team and Crosby is the best player in it. Who cares if theres an advantage, every single Capitals fan wishes he was playing.
But since he isn't, the pressure is higher and the Capitals must do everything they can to tie this series tonight.