Champions League holders Barcelona saw their perfect start to the season ended after they were held to a 1-1 draw by Roma at the Stadio Olimpico in Wednesday's Group E opener.
Luis Suarez gave Barca a 21st-minute lead but Roma equalised eight minutes later with a wonder goal from defender Alessandro Florenzi.
Florenzi drilled a right-footed shot from just over the halfway line and the ball cannoned into the back of the net off a post.
Barca had plenty of chances to move back in front and were unlucky not to do so in the 78th minute when Lionel Messi, making his 100th Champions League appearance, saw his left-footed shot from the right side of the area hit the crossbar.
Roma held on for a point to deny their former coach Luis Enrique a perfect start to the competition.
Barca started brightly and sent an early warning when Messi got past his marker and drilled a left-footed effort over the bar.
Daniele De Rossi made a vital block from Messi's goal-bound attempt in the 18th minute as Barca got closer, and three minutes later the visitors moved in front through Suarez.
The Uruguay forward met Ivan Rakitic's deflected cross at the far post with a header to beat Roma goalkeeper Wojciech Szczesny.
Barca demanded a penalty in the 24th minute when Suarez went down in the area following contact from Szczesny, but the referee waved play on.
Roma pulled level soon after thanks to a brilliant long-range effort from Florenzi that gave visiting goalkeeper Marc-Andre ter Stegen no chance.
Barca reacted well and began to exert control as Messi saw several long-range attempts go over the bar.
The Argentina captain continued to torment the Roma defence and in the 38th minute, Messi got past his marker and struck a low shot from 12 yards that was only just kept out by Szczesny.
Messi picked up where he left off after the restart, but he was once again thwarted by Szczesny as his fine effort from the edge of the area was saved.
Roma's hopes looked to be dwindling when Rudi Garcia was forced to make his first substitution six minutes after the break, with Szczensy picking up an injury with Morgan De Sanctis replacing him.
Barca surged forward and in the 76th minute Neymar came close to scoring, but saw his goal-bound shot from the heart of the area blocked by Roma defender Kostas Manolas.
Two minutes later Roma had fortune on their side when Messi hit the bar with De Sanctis beaten, but the former Napoli keeper was at his best to repel Andres Iniesta's close-range shot.
With seconds remaining, Jordi Alba fed Neymar in the box and his effort was blocked by Manolas as Roma held on for a valuable point.