Verratti, along with fellow Italy international Alessandro Florenzi, missed the first meeting between the teams in Munich after testing positive for COVID-19.
However, the duo have received the all-clear and are back in training ahead of the return fixture in the French capital, with PSG holding a 3-2 advantage at the halfway stage in the tie.
Pochettino told the media on Monday he is yet to decide on his line-up, with Marquinhos remaining a doubt due to a thigh injury.
"We haven't decided the team for tomorrow yet, but it will be difficult for Verratti to start," the PSG boss said in his pre-game news conference. "Florenzi will be assessed further tomorrow."
On Marquinhos' status, he added: "We will see how he feels tomorrow. In theory, he could be involved in the squad, so we will see.
"I don't think he will be able to start, certainly, but he may be able to be on the bench. We will decide that on Wednesday."
PSG knocked out Barcelona in the previous round 5-2 on aggregate, though were held to a 1-1 draw at home in the second leg following a resounding triumph at Camp Nou.
Pochettino is well aware that the tie with Bayern – who he made clear are the best team in the world – is much tighter, meaning his players must find the right balance between retaining their slender advantage and also posing problems in attack for their opponents.
"At home to Barcelona, particularly in the first half, we found it very hard to keep the ball, even with Verratti and Leandro Paredes in the team," Pochettino said.
"It is not about individual names but collective attitude. We have to have a different approach from the Barcelona game while understanding that we don't just need to defend but also to keep the ball to attack and hurt the opposition.
"This is the challenge that lies ahead, and once again we have a positive first-leg result to build on."
PSG have won all four of their previous games in which they have hosted the German side in European competition, while only three of the previous 50 teams to lose the first leg at home in a Champions League knockout tie have managed to progress.
Pochettino, though, is well aware of the size of the task the hosts face against the defending champions, with Bayern having gone 16 games unbeaten in the competition under Hansi Flick prior to the loss on home soil last week.
"The Barcelona game is the past, Bayern are the best team in the world at the moment so they will certainly make it difficult for us," the former Tottenham head coach said.
"We need the strength and ability to manage those moments, just as we did in the first leg in Munich.
"They are world champions who have won six trophies in recent months. We are the pretenders and contenders to win the trophy. We have to consider all the circumstances surrounding the tie.
"If we get through to the semi-finals, it will be a big achievement for the club. PSG want to win every competition we are involved in, but beating Bayern Munich, in itself, would be a big feat."