The hosts have already knocked Compostela and Celta Vigo out of this year's tournament and are yet taste defeat in any competition so far this season.
A Celta Vigo side without Iago Aspas spearheading the attack will always struggle for goals, but not many supporters could have expected Ibiza to put five past the La Liga outfit in the second round of the Copa del Rey.
Celta's makeshift defence shipped three goals to the minnows before half time and ultimately suffered a 5-2 defeat to Ibiza, who are participating in just their third ever Copa del Rey campaign after being knocked out at this stage by Barcelona last season.
Juan Carlos Carcedo has overseen a magnificent start to the season for Ibiza, who are well on their way to the promotion groups from Segunda Division B with eight wins and two draws from their 10 league outings so far.
This week's hosts have only shipped four goals across all competitions this season and have marched to victory in every home game so far - including a 1-0 victory over Levante II at the weekend courtesy of Sergio Cirio's winner.
Carcedo's men follow up the visit of Athletic with a league trip to struggling La Nucia, and with the healthy seven-point lead that Ibiza boast at the top of the table, they can certainly afford to go for broke in an attempt to dump another top-flight team out of the competition.
That will certainly be easier said than done, though, as Athletic have already claimed one piece of silverware this season in the form of the Supercopa de Espana and are pining for more.
Marcelino has taken just two-and-a-half weeks to steer Athletic to their first trophy since the 2015-16 season, with Inaki Williams scoring a goal worthy of winning any final as Thursday's visitors eked out a 3-2 win over Barcelona in extra time.
Athletic have now beaten both Real Madrid and Barcelona in the space of a week, but despite their remarkable start to life under Marcelino, they cannot afford to underestimate an equally dominant Ibiza outfit - especially as they are on a seven-game losing run away from home.
Les Leones have lifted the Copa del Rey 24 times down the years - only Barcelona have won more - and incredibly, they are still waiting to play last year's final against Real Sociedad after the coronavirus pandemic devastated the sporting calendar.
For now, though, Athletic will hope to avoid being knocked out of this year's tournament before they finish playing last year's, and Thursday's game represents the first ever meeting between Ibiza and Los Leones.
UD Ibiza Copa del Rey form: WW
UD Ibiza form (all competitions): DDWWWW
Athletic Bilbao form (all competitions): DLWLWW
Ibiza defender Ruben Gonzalez was forced off just before the half-time whistle blew against Levante II, and it would be a surprise to see the 26-year-old return in time for this one.
Atletico Madrid loanee Sergio Castel struck twice against Celta Vigo to take his tally across all competitions to six for the season, and the 25-year-old will be tasked with breaching an intimidating Athletic defence.
Full-back Yuri Berchiche missed out against Barcelona but is back in training alongside Lopez, although Marcelino is expected to shuffle the pack considerably for this bout.
UD Ibiza possible starting lineup:
Parreno; Grima, Pardo, Goldar, Morillas; Molina; Perez; Lopez, Lara, Davo; Castel
Athletic Bilbao possible starting lineup:
Ezkieta; Lekue, Nunez, Alvarez, Balenziaga; Vesga, Vencedor; Gomez, Sancet, Berenguer; Villalibre
We say: UD Ibiza 1-3 Athletic Bilbao
Ibiza's rearguard is incredibly well-drilled and a reshuffled Athletic attack will not have it all their own way at the Estadi Municipal de Can Misses. However, the challenge that the hosts could present will be futile compared to that of a full-strength Real Madrid or Barcelona - both of whom Athletic have overcome - so we expect a straightforward win for Marcelino's men in this third-round encounter.