Napoli lost 3-1 on Tuesday night, the second leg is at the Stadio San Paolo on March 7.
“At the start of the game they immediately attacked us, forcing Pepe Reina into a great save, but we reacted strong with a fantastic curler from Insigne that surprised Keylor Navas," wrote Hamsik on his official website.
“In the second half, they found two goals in the opening five minutes. We do feel regretful, because over the course of the game we went close to a second goal.
“Naturally we have played better than we did yesterday, but we cannot forget that we were facing one of the best teams in the world.
“We are sad, but getting an away goal could be important. We'll continue to try our best and in the second leg anything is possible."