The two, who face Spartak Moscow and PSV Eindhoven respectively, will be in vastly different moods after Porto won 2-1 at Benfica on Sunday in a heated "classico" to clinch the league title with five matches to spare.
Benfica's match is a repeat of the 1988 European Cup final which the Dutch side, then coached by Guus Hiddink, won on penalties after a 0-0 draw.
Braga, the third of the Portuguese trio and conquerors of Liverpool in the last round, visit Dynamo Kiev and Spain's Villarreal, the only representatives from any of the major European leagues, host Dutch league leaders Twente Enschede.
Porto barely had time to celebrate Sunday's win before continuing on their quest to complete what would be a league, cup and Europa League treble.
Under the leadership of 33-year-old Andre Villas Boas, the Dragons have had an astonishing season, winning 23 and drawing two in 25 league matches.
Inspired by Colombian pair Fredy Guarin and Radamel Falcao and the burly Brazilian striker Hulk, their Europa League campaign has been nearly as impressive with 10 wins, a draw and a defeat in 12 outings and 26 goals scored.
Spartak coach Valery Karpin witnessed Sunday's win in the Estadio da Luz and was impressed by what he saw.
AMAZING QUALITY
"They came to the stadium of their great rivals and were crowned champions," he told the Portuguese sports daily A Bola. "They demonstrated they barely have any weak points.
"I was really amazed with the quality of their players and team," added Karpin, whose neighbours CSKA were eliminated by Porto in the previous round.
Villas Boas, once an assistant to Jose Mourinho, is already being compared to his former boss and Porto's real challenge could be to hold on to their key names when the season ends.
Benfica's indignation at seeing their great rivals celebrate in their own stadium has been followed by the news that 34-year-old striker Nuno Gomes is out for the rest of the season with a knee ligament injury.
The once-mighty Eagles, who like Porto depend heavily on a large South American contingent, are attempting to reach their first European semi-final in 17 years.
Villarreal have a 100 percent European home record this season in their favour as they host Twente, who like Spartak Moscow, Benfica and Braga parachuted into the Europa League knockout stages after failing to qualify from their Champions League group.
"We know we can go to any stadium in Europe and get a win while at home we are very strong," said Villarreal goalkeeper Diego Lopez, who has been ever-present.
"In the last two rounds, we did well against two very tricky sides and now we face Twente. The tie will be very open with both teams believing they can get through."
Dynamo Kiev are without Serbian midfielder Milos Ninkovic for the visit of Braga, who lost twice to Ukraine's Shakhtar Donet
