Another debut goal from Alexandre Pato proved in vain as Villarreal lost 2-1 to Monaco, while Thomas Vermalen was sent off in his Roma bow.
Alexandre Pato continued his extraordinary record of scoring on his debuts as he struck in Villarreal's 2-1 defeat to 10-man Monaco in the first leg of their Champions League qualifying play-off.
The forward, who has previously netted in his maiden appearances for Inter, AC Milan, Corinthians, Chelsea and Brazil, opened his Villarreal account 36 minutes into his El Madrigal bow, restoring parity following Fabinho's earlier penalty.
However, the LaLiga side - now managed by Fran Escriba following Marcelino's departure - could not build on Pato's leveller, with Portugal playmaker Bernardo Silva doing the damage for Monaco, who had Benjamin Mendy sent off late on.
Elsewhere, Celtic survived a second-half scare to secure an ultimately comfortable 5-2 home victory over Hapoel Be'er Sheva at Celtic Park.
Brendan Rodgers' side had taken a convincing first-half lead courtesy of a Tom Rogic strike and Leigh Griffiths' brace, but they were almost pegged back when the visitors netted twice in the space of two minutes shortly after the restart.
Fortunately for the hosts, Moussa Dembele was on hand to extend their slender advantage just three minutes after coming off the bench, with captain Scott Brown wrapping up the win late on and handing Celtic a three-goal cushion in the tie.
Meanwhile, Thomas Vermaelen's Roma debut ended prematurely as he was sent off after just 41 minutes against Porto, though his side did manage to hold out to claim a hard-fought 1-1 draw at the Estadio do Dragao.
In Wednesday's other fixtures, Dundalk slipped to a 2-0 home defeat to Legia Warsaw, while Ludogorets eased to victory against Viktoria Plzen.