Madrid: The Iberian peninsula's grip on the Europa League will loosen if Juventus and Basel can make good on first-leg victories and reach the semifinals of Europe's second-tier tournament.
Juventus' 1-0 first-leg win at Lyon provides the cushion of an away goal for the Serie A champions at their home stadium, where the final will be held on May 14.
Basel trounced Valencia 3-0 to travel to Spain with a big lead, while Benfica and Porto both secured 1-0 victories for the Portuguese clubs to be in control of their series.
Portuguese leader Benfica welcomes AZ Alkmaar while Porto travels to Sevilla with the confidence of knowing three of the past four winners of the competition have come from Spain or Portugal.
Here are five things to know about Thursday's quarterfinal return legs:
HOME SWEET HOME: Juventus has been unbeatable at home this season and will expect to continue that record following its 1-0 first-leg win at Lyon.
A 2-0 victory over Livorno on Monday marked Juve's 16th win in 16 Serie A home matches this season, matching the record set by city rival Torino in 1947-48.
Juventus is undefeated at home in its other three competitions this season as it hones in on a third consecutive Italian title with an eight-point lead over Roma. It just has to be sure it reaches the Europa League final, next.
"We want to get into a European semifinal," Juventus coach Antonio Conte said. "We need the support of our fans, from now until the end of the season."
SWISS CAN'T MISS: Basel is playing for national pride -- and its own future Champions League prospects -- at Valencia on Thursday.
Leading 3-0 from the first leg at home, Basel is favored to advance to a second straight Europa League semifinal and earn Switzerland extra ranking points. That would lift the Alpine nation into 12th place in UEFA's rankings for club competitions -- guaranteeing whoever is Swiss league winner next year a place in the 2015-16 Champions League group stage.
Basel has won five of the past six Swiss titles and currently leads the table.
VALENCIA FREEFALL: Valencia is in danger of missing out on European football altogether for the first time since the 2005/06 season.
The 0-0 draw at Valladolid on the weekend left it winless in five matches in all competitions. Valencia is eighth in the Spanish league, nine points off qualifying for the next season's Europa League with just six games to play.
"The last thing we will lose is our hope," Valencia coach Juan Antonio Pizzi said.
PORTO HOPES: Porto carries a 1-0 first-leg lead to Sevilla where it will aim to make up for its disappointing reign as Portuguese champion.
Porto was mathematically eliminated from the domestic title race on Monday when it dropped 15 points behind leader Benfica. Porto warmed up for Sevilla with a 3-1 victory over Academica.
Sevilla's chase for one of the Spanish league's Champions League places continued gaining steam as it beat Espanyol 4-1.
"The team is ready, it believes in its chances," Sevilla coach Unai Emery said. "But Porto is a team that is always capable of creating problems, so we have to expect they will be at their best."
BENFICA REBOUNDS: Benfica is on course to erasing all of last year's disappointments as it welcomes Dutch side AZ Alkmaar nursing a 1-0 lead.
The Portuguese leaders went from treble talk to zero trophies last season after being undone by late goals in all three competitions, ultimately losing the Portuguese title to Porto, the Portuguese Cup to Guimaraes, and the Europa League to Chelsea following a stoppage-time winner.
Now, Portuguese leader Benfica enjoys a six-point advantage over Sporting Lisbon after a 4-0 win over Rio Ave on Monday.
"We're playing well, with great confidence and good execution," Benfica defender Maxi Pereira said.