Twice former winners Porto qualified for the knockout stages of the Champions League after drawing 0-0 with Dynamo Kiev at the Olympic Stadium on Tuesday.
Group A leaders Porto have 10 points from four games, one in front of Paris Saint-Germain and six ahead of Kiev. Dinamo Zagreb are bottom without a point.
"With their supporters behind them Dynamo are dangerous at home but the result was fair," Porto coach Vitor Pereira told reporters.
"Not every team can achieve qualification on matchday four."
Zlatan Ibrahimovic laid on all four goals as PSG beat Zagreb 4-0 in Paris on Tuesday.
Having survived some early pressure, Porto started to take control of the midfield.
Jackson Martinez went close for the 1987 and 2004 champions when he forced keeper Maxym Koval into a stunning save from a header that seemed destined for the bottom corner of the net.
Goal chances were few and far between in the first half but James Rodriguez set up Porto team-mate Silvestre Varela early in the second half only for the midfielder to hit the outside of the post.
Kiev carved out two good opportunities midway through the second period.
Andriy Yarmolenko broke down the right and shot weakly straight at Helton and the same player was denied again by the keeper from a header moments later.
The Ukrainians built a promising attack in the closing stages but the move had to be halted when a fan suddenly invaded the pitch and had to be taken off the field by security guards.
Kiev coach Oleg Blokhin, who turned 60 on Monday, is still recovering after undergoing surgery a month ago and watched the game from the stands.
"I cannot say we are happy with the result. We had hoped for a win," said assistant coach Olexiy Mykhailychenko.
"We still have a theoretical chance of qualifying for the next round and we will keep on fighting for the points."comments