Marc-Andre ter Stegen was Barcelona's hero as he saved a penalty to ensure they returned from Borussia Dortmund with a hard-earned 0-0 draw in their Champions League opener.
Ter Stegen kept out Marco Reus' 57th-minute spot-kick after Jadon Sancho had been fouled by Nelson Semedo, although he later needed the help of his crossbar to keep out Julian Brandt's long-distance piledriver.
It finished 1-1 in the other game in Group F after substitute Nicolo Barella came to Inter Milan's rescue with an injury-time equaliser to deny Slavia Prague victory.
The Serie A leaders were trailing to Peter Olayinka's 63rd-minute strike when, seconds after Stefano Sensi had rattled the bar with a free-kick, Barella levelled to snatch a draw.
Last season's semi-finalists Ajax cruised to s 3-0 Group H victory over Lille after Quincy Promes had headed them into an early lead.
Second-half goals from Edson Alvarez and Nicolas Tagliafico completed the job as the Eredivisie leaders eased past their Ligue 1 rivals.
Valencia joined them on three points after Chelsea's Ross Barkley fluffed a late penalty to condemn manager Frank Lampard to defeat on his Champions League debut as manager.
The Blues, trailing to a goal from Valencia winger Rodrigo, were given a lifeline in the closing stages when VAR flagged up a handball in the area, but Barkley's spot-kick clipped the crossbar and his side went down 1-0.
In Group G, Timo Werner's late double proved enough for RB Leipzig to get their campaign up and running with a 2-1 victory at Benfica.
Werner struck twice inside nine second-half minutes to put the visitors in the driving seat, although they had to see out a tense conclusion after Haris Seferovic reduced the deficit with six minutes remaining.
Memphis Depay's penalty ensured Lyon emerged from their opening Group G fixture against Zenit St Petersburg with a 1-1 draw.
Sardar Azmoun had put the visitors ahead four minutes before the break, but Depay ensured it finished all square when he converted from the spot with 51 minutes gone after he had been fouled by substitute Magomed Ozdoev, who failed to redeem himself when he missed with a close-range 70th-minute header.
Fernando Llorente gained revenge for last season's Champions League final defeat by Liverpool with a late goal to seal a 2-0 defeat for Jurgen Klopp's men against Napoli.
The former Tottenham frontman struck in stoppage time after Dries Mertens had opened the scoring from the penalty spot with eight minutes remaining at the Stadio San Paolo after Andy Robertson had tripped Jose Callejon.
Group E rivals Red Bull Salzburg turned in the performance of the night as they thumped Belgian champions Genk 6-2.
Striker Erling Haaland plundered a first-half hat-trick with efforts from Hwang Hee-chan and Dominik Szoboszlai making it 5-1 at the break after John Lucumi had pulled one back.
Mbwana Samatta further reduced the deficit after the break, but Andreas Ulmer completed the rout.