The first-leg clash on Wednesday takes place 10 days on from Barca securing an absorbing 3-2 win over Villarreal on home turf in La Liga, despite twice falling behind.
Denis Cheryshev and Luciano Vietto put Villarreal in front either side of half-time, but goals from Neymar, Rafinha and Lionel Messi saw Luis Enrique's team over the line.
It was as tough an examination as Barcelona have endured during a run of nine consecutive wins in all competitions that includes their quarter-final victories over Atletico Madrid.
Messi has scored 10 goals in nine matches since the turn of the year and the mercurial Argentinian was influential in Sunday's swashbuckling 5-2 La Liga win at Athletic Bilbao.
Luis Suarez has found goals harder to come by in during his debut season in Spain, but Messi set him up to fire home Barca's second at San Mames.
The Uruguay international trained on Monday despite limping out of Sunday's game late on, having been on the end of an ugly challenge that saw Xabier Etxeita receive a straight red card.
Victory in Bilbao took Barcelona through the 100-goal barrier for the season and club president Josep Maria Bartomeu praised the team's improvement since a surprise defeat to Real Sociedad at the start of last month piled pressure on Luis Enrique.
"The team is good and getting better every day," he told AS. "The fans will be happy because the team is improving. The change is obvious.
"We're reaching the level we want to be at and we can have a very good year.
"There haven't been any new players or a new coach to work with the group. We found our rhythm and the evolution is positive. I think we can still improve our level."
Elsewhere, Barcelona full-back Martin Montoya missed training due to illness on Monday.
Andres Iniesta was an unused substitute at the weekend and could feature from the start alongside Rafinha if Luis Enrique opts to refresh his line-up.
Defeat at Camp Nou earlier this month is Villarreal's only loss of 2015 and the remaining five of their past six matches ended in victory.
Mateo Musacchio opened the scoring before a late Gerard Moreno effort sealed a 2-0 win over Granada on Saturday that leaves Marcelino Garcia Toral's team sixth in La Liga.
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