Busquets and Alba follow Gerard Pique in taking a salary reduction to enable their financially troubled club to register new players and fit into the league's strict financial fair play regulations.
Earlier on Sunday, August 8, Lionel Messi confirmed the end of his 21-year stint with Barcelona as he was left in tears while saying goodbye to his boyhood club.
"It's a shame, we would've have liked for our tournament not to end today but that's football," Busquets told Radio Marca.
Italy is Europe's hottest team, extending its unbeaten run to 32 matches and its winning streak to 13 with Friday's result. Spain is on a 12-match unbeaten run and drew its opening two Euro games.
Vladimir Petkovic's side recovered from two goals down to force extra time against much-fancied France and prevailed on penalties.
All eyes will be on Croatia's Luka Modric for his goal-scoring and Spanish Striker Alvaro Morata for the lack of it.
Sergio Busquets had to pause for a moment while talking about his time away from the squad because of the coronavirus.
Sergio Busquets will be in Seville for Spain's match against Poland, though he is not likely to play after not practicing regularly while in isolation.
Spain captain Sergio Busquets is still self-isolating at home while defender Diego Llorente was only allowed to rejoin the group on Saturday after giving a fourth consecutive negative test.
Scotland will face the Czech Republic in Glasgow on Monday, before a new-look Spain get their bid for a record fourth European crown underway without captain Sergio Busquets.
Sergio Busquets left the team's pre-Euro 2020 training camp on Sunday, while the rest of the squad tested negative after their friendly draw with Portugal in Madrid at the weekend.
Busquets will need to be in isolation for 10 days, and his participation in the European tournament is in doubt.
Barcelona midfielder Sergio Busquets reiterated his call for the club's board to strengthen in the transfer market.
Barca have been heavily linked with moves for Liverpool's Philippe Coutinho and Ousmane Dembele of Borussia Dortmund.