A Dimitris Salpigidis penalty proved enough to seal a narrow 1-0 Europa League victory for Panathinaikos over Sturm Graz in a tightly-contested encounter at the Olympic Stadium in Athens.
The Greece international slotted home on the hour after being upended by Mario Sonnleitner and despite chances for both teams as the game opened up afterwards, Henk ten Cate's men claimed the three points.
The win means Pana remain second in Group F, one point behind Galatasaray, who defeated Dinamo Bucharest 4-1.
While monopolising much of the first-half possession, Panathinaikos failed to fashion any clear-cut chances as their final pass let them down, Salpigidis in particular disappointing with his crosses from the right.
It was no surprise then that the visitors, playing a counter-attacking game, were the first to threaten when Haris Bukva fired into the side netting from Peter Hlinka's cross.
Sebastian Leto with his penetrating runs down the left was the hosts' main outlet and he was twice denied by Sturm keeper Christian Gratzei with shots from the edge of the box.
The best chance of the opening 45 minutes fell to Sturm though when Manuel Weber was put clean through on goal from Samir Muratovic's quickly-taken free-kick but blazed over with only home keeper Alexandros Tzorvas to beat.
Ten Cate introduced Sotiris Ninis at half-time in an attempt to add attacking impetus and the 19-year-old's enthusiasm seemed to spark the Greens into life, Djibril Cisse shooting narrowly wide under pressure from Gabriel's right-wing cross three minutes after the restart and Loukas Vintra trying his luck from distance.
The breakthrough finally came on the hour when Salpigidis surged into the penalty area before being fouled by Marios Sonnleitner.
Salpigidis dusted himself down to slot his penalty beyond Gratzei and into the bottom left corner.
The goal seemed to galvanise both teams with Sturm's Gordon Schildenfeld heading against Tzorvas' left post before Karagounis responded by cracking an effort off Gratzei's right post seconds later.
Tzorvas was then called into action to make a superb double save from Sturm striker Daniel Beichler, who twice failed to convert Jakob Jantscher's free-kick.
Pana responded through Cisse whose powerful shot was brilliantly diverted over the crossbar by Gratzei's sprawling save. The Frenchman, who had a disappointing match, then blazed a shot wide from 12 yards out with just Gratzei to beat in the last minute.