Paris (AFP) - Ten-man Arsenal were left frustrated after a 0-0 stalemate at Besiktas in Tuesday's Champions League play-off round first leg while Athletic Bilbao earned the upper hand in their tie with Napoli following a 1-1 draw in Italy.
Ba again tested Szczesny with a firmly-struck volley while Olivier Giroud and Santi Cazorla went close for the Gunners before Ba, who scored a hat-trick versus Feyenoord in the previous round, rolled a shot just wide of the post at the end of a lively opening 45 minutes in Turkey.
Olcay Sahan spurned a glorious chance to put Besiktas in front early in the second half much to the chagrin of coach Slaven Bilic while Arsenal boss Arsene Wenger will have to do without midfielder Aaron Ramsey in next Wednesday's second leg after the Welshman was dismissed for a second bookable offence 10 minutes from time.
Arsenal nearly snatched victory in the closing stages but Tolga Zengin made a superb save to tip substitute Alex Oxlade-Chamberlain's effort onto the post and keep Besiktas very much in the tie.
Athletic Bilbao secured a vital away goal through Iker Muniain just before the break in Naples and go into the return leg next Wednesday at San Mames as slight favourites despite Gonzalo Higuain netting a 68th-minute equaliser for Napoli in a 1-1 draw.
Stefan Kiessling, Karim Bellarabi and Heung-Min Son were on target for Bayer Leverkusen side in Denmark as Roger Schmidt's men earned a 3-2 victory away to FC Copenhagen.
Mathias Joergensen had cancelled out Kiessling's opener before Daniel Amartey put the Danes in front but strikes from Bellarabi and Son put Leverkusen in control of the tie.
Goals in either half from Franz Schiemer and Jonathan Soriano earned Austrian champions Salzburg a 2-1 win at home to Malmo but Emil Forsberg's injury-time strike gave the Swedes a fighting chance of reaching the Champions League group stage for the first time.
1986 European champions Steaua Bucharest take a 1-0 advantage into the return leg against Bulgarians Ludogorets after Alexandru Chipciu struck an 88th-minute winner for the Romanian side.