The Rossoneri fell 1-0 at home to the Spanish side on Tuesday in the first leg of their Champions League last 16 tie.
Milan travel to the Vincente Calderon stadium for the return leg on March 11.
"I am very happy with my players' performance," Seedorf said. "I think a goalless result would have been a fair outcome.
"But there is still the return leg left to play and our fans and our players can be optimistic.
"I saw a lot of positives from my team and we must continue to work hard in order to improve.
"Now we must turn our attention to Serie A and bring three points home on Sunday."
Mario Balotelli, who is Milan's top scorer, is expected to shake off a right shoulder injury sustained against Atletico and lead Milan's attack this weekend.
Balotelli scored his 10th league goal in last Saturday's 1-0 triumph over Bologna.
The victory was Milan's eighth of the campaign and lifted the Rossoneri to ninth place, seven points behind city rivals Inter Milan, who hold the last European qualifying spot.
Rivals Sampdoria must overcome the absence of defenders Lorenzo De Silvestri and Daniele Gastaldello.
Both players were booked in last weekend's 3-0 defeat at Roma and must serve a one-match ban, much to coach Sinisa Mihajlovic's disappointment.
"They could have easily avoided being booked against Roma," he said. "It's annoying to have to do without them for such a big game."
Last weekend's reverse dropped Samp to 12th in the standings, nine points above the drop zone.
Samp are unbeaten at the Luigi Ferraris stadium since November 2.
The Blucherciati are hoping to recover Argentinian striker Maxi Lopez in time for the match with the former Rossonero player sidelined with a left foot injury.
AC Milan full back Mattia De Sciglio is sidelined with a sprain in his right ankle.