Real Madrid ground out a 2-0 victory at Wisla Krakow and Manchester United needed an own goal to scrape a 2-1 win at Dinamo Bucharest in Champions League third qualifying round first leg matches on Wednesday.
There was frustration for two other favourites bidding for a place in the lucrative group phase when Inter Milan drew 1-1 in Basel and last season's semi-finalists Deportivo Coruna were held to a shock 0-0 draw by Shelbourne in Dublin.
There were no such problems for last season's finalists Monaco, who trounced Nova Gorica of Slovenia 3-0 with 10 men, or Bayer Leverkusen who thrashed Banik Ostrava 5-0, while 1991 champions Red Star Belgrade edged PSV Eindhoven 3-2 at home.
Real were rescued by two goals from substitute Fernando Morientes, back with the Spaniards after becoming the Champions League's top scorer last season with nine goals while on loan at French club Monaco who he helped to reach the final.
Morientes got the breakthrough in the 72nd minute off a cross from England skipper David Beckham and put the result beyond doubt in the 90th minute, steering home a ball from Brazil defender Roberto Carlos.
Real, starting the long road to a potential 10th European crown, should easily finish the job in the second leg at the Bernabeu in a fortnight's time.
United are also well-placed after a side weakened by injuries, suspension and Olympic duties, recovered from a Quinton Fortune own goal after 10 minutes to beat Dinamo.
Ryan Giggs raced through for a well taken goal in the 38th minute and after new striker Alan Smith hit the post, United finally got their win when Dinamo defender Angelo Alistar put substitute Liam Miller's cross into his own net in the 71st.
Inter have the safety net of the away goals rule for the second leg at the San Siro after a superb solo strike from their Brazilian striker Adriano was cancelled out by Benjamin Huggel's equaliser for Basel after 25 minutes.
Shelbourne, the first Irish side to reach the third qualifying round, fully deserved their draw at Lansdowne Road after dictating much of the play against Deportivo.
Striker Mohamed Kallon scored two of Monaco's goals in their victory over Nova Gorica, while Franca scored a hat-trick in Leverkusen's rout of Banik Ostrava.