The former Blaugrana assistant coach argued the forward had "lost his passion for football" but the Argentina international insists the comments were without foundation.
The 67-year-old Argentine, who worked under former Blaugrana boss Cesar Luis Menotti at Camp Nou in the 1980s, suggested earlier this month that his compatriot had "lost his passion for football" after becoming bored of his "15-year marriage" to the sport.
However, Messi, who only recently recovered from a hamstring injury, insists he remains "dedicated" to playing.
"I don't give any importance to Cappa's comments. I don't know why he said that. I'm thinking about getting back to my level," the four-time Ballon d'Or winner told Radio La Red. "I'm dedicated to playing. When I wasn't scoring, I was happy with my performance. I know what I give to, and how I feel about, football.
"I took the injury calmly. It took a long time to be ready, but now I'm not rushing things. As matches go by, I'm feeling better. It's how we planned."
Messi went on to praise coach Gerardo Martino for the way he has grown accustomed to life at the helm of the Blaugrana.
"He's gradually learning the club, the media, the fans, everything. Beyond what he knows as a coach, Tata is a very intelligent person, and he knows how to handle all this," he said.
It had been suggested Martino could experiment with the Barca set up by deploying Messi in a deeper or wider role in attack, but the 26-year-old himself says his position remains more or less the same as it has been since former boss Pep Guardiola first moved him to the center of the forward line.
"I heard in various places it had been said I would be playing further behind or in a different position," Messi stated. "We keep playing without a No.9, we still use a 'false nine' as we used in Guardiola's era. The position remains the same."