The Uruguayan was sanctioned after he was cited by the referee for causing a post-match altercation in the tunnel, per Spanish football writer Rik Sharma:
Rik Sharma @riksharma_
Ref report says Suarez lurked in the tunnel to goad Espanyol players after game, shouting "you're a waste of space" https://t.co/RKKidGCkIX2016-1-6 22:59:53
He subsequently missed the return leg—which Barca won 2-0 to advance 6-1 on aggregate—and will be absent for the quarter-final first leg against Athletic Bilbao on Wednesday unless the Blaugrana's appeal is successful.
But Suarez is adamant he has nothing to apologise for, per Goal.com: "About the sanction, I don't know if I will play but my conscience is clear because I did not say anything."
Per Sport, Barcelona are insistent Suarez did not say what he was accused of saying by the referee.
Their first appeal against his ban was rejected by the Spanish Football Federation, but Barcelona have now taken the case to the Disciplinary Committee for Sports in an attempt to have Suarez available for the Athletic clash, per the club's website.
Suarez netted a hat-trick against the Bilbao outfit in La Liga on Sunday as Barca ran out 6-0 winners.
The Catalans can likely beat Athletic again in Wednesday's first leg at San Mames Stadium even without Suarez, but they clearly feel the ban is unwarranted.
The 28-year-old has become a key star for Barca since joining the club from Liverpool in 2014, and the Camp Nou team will miss his immense goalscoring should he be unable to play in the first leg.
No other player in Europe's top divisions has scored more goals in all competitions this season, per Opta:
29 - Luis Suárez has scored more goals than any other player in the top five European leagues (all competitions). Monster.2016-1-17 21:18:07
And, despite his glaring omission from the recently announced FIFA/FIFPro World XI, there is little doubt he is one of the world's best strikers, per Bleacher Report's Dean Jones and Sam Tighe:
He is no stranger to controversy, having picked up several lengthy bans during his career, including long suspensions for biting on more than one occasion.
However, Suarez has avoided the negative spotlight for much of his Barca career and only made headlines for his on-pitch performances.
He clearly is not happy with being slapped with a two-match ban on this occasion for something he claims not to have done, but his chances of winning his appeal seem slim.