It is not yet known if Messi will be fit for the quarter-final second leg after suffering a hamstring injury during last week's 2-2 first leg draw in France, a problem that kept him out of Saturday's league win over Real Mallorca.
Losing Messi would be a huge blow for the Catalan giants as they seek a place in the semi-finals, but Thiago Silva feels Barca coach Tito Vilanova has more to ponder at the other end of the pitch.
Javier Mascherano also picked up a knee injury at the Parc des Princes that has seen him ruled out for six weeks, while Carles Puyol and Adriano have both been sidelined and Eric Abidal only recently returned to action after from more than a year out having undergone a liver transplant.
Thiago Silva, who has declared himself fit for the match after a slight knee problem, told El Mundo Deportivo: "I think Barca have a bigger problem with the absences of Puyol and Mascherano than that of Messi, even though Leo isn't ruled out.
"They have to improvise at the back and that complicates things a little for them, although Barca are always Barca."
On the prospect of Messi possibly being ruled out, the Brazil international added: "It's true that if he doesn't play it would be a relief for me, but not totally because they have (David) Villa), Pedro...
"Barca don't only have the best player in the world, they also have the best team."
PSG twice trailed in the first leg but gave themselves a fighting chance heading to the Nou Camp thanks to late equalisers from Zlatan Ibrahimovic and Blaise Matuidi.
Despite that though, Thiago Silva concedes his side have a job on their hands to progress through.
He said: "Barca are always the favourites, whoever they are playing and whatever score they've got.
"They are a team who have earned respect for their football and for all that they've won in recent years.
"For me they are the best team in the world.
"I enjoy watching them play and now disappointingly we've been drawn against them and one of us must be knocked out. I hope they don't ruin our European dream."