The Argentine attacker went off at halftime with a hamstring strain in the first leg in Paris on Tuesday, but is training in hopes of returning for Wednesday's second leg.
Messi was withdrawn at halftime at the Parc des Princes after pulling up late in the first period, by which time he had already given Barca the lead in the first-leg match, which finished 2-2.
Thursday was a day off for the Barcelona squad, but Messi turned up for a double session with physio Juanjo Brau and is keen to play the return match versus PSG.
Tests on Wednesday revealed the problem to be less serious than the club had initially imagined, with the original prognosis estimating that the Argentine would be sidelined for around three weeks.
But Messi allayed fears as he wrote on his official Facebook page: "I will be back soon, luckily it [the injury] wasn't much."
The 25-year-old Messi will miss Saturday's match at home to Mallorca in La Liga, thereby ending his run of 19 consecutive rounds on the scoresheet. Messi has benefited from the Catalan club's calendar in that its match in Paris was played on Tuesday, with the return scheduled for Wednesday - an eight-day gap, as opposed to Real Madrid's six-day break between its two games against Galatasaray.
Adriano also has an outside chance of returning on Wednesday as well, as Barca hopes to bring back defenders to ease the current crisis, with Carles Puyol sidelined following a knee operation and Javier Mascherano stretchered off with ligament damage against PSG.