The former Genoa man is eagerly anticipating this week's return leg, and is confident that the Rossoneri can make it to the quarter-finals
The Serie A outfit recorded a 2-0 victory at San Siro in the first leg of the round of 16 tie, but Constant expects a tough night's work in the second meeting between the two sides.
"We’re all focused on the match against Barcelona. We’re well aware that Tuesday’s match will be very different to the first leg," Constant told Milan Channel.
"We start with a 2-0 lead but we won’t be going there just to defend. We’ll have to take to the field with the right mentality. They’ll have a lot of possession but when we get on the ball we’ll have to make it count.
"Barcelona are a great team but they’re going through a tough period. It happened to us as well at the start of the season but we’ll have to be wary of playing the best team in the world."
The wing-back then went on to stress that he's confident Milan have what it takes to make it to the quarter-finals.
"I’m convinced that we’ll play a good game and get through to the next round, though. We’ll have to make the most of the advantage that we have.
"They’ll try and attack from the outset and try to score as quickly as possible and we’ll have to be ready for that mentally."
Tuesday's encounter is scheduled to kick off at 20:45CET.