The absence of Lionel Messi and Luis Suarez hampered the holders' hopes of extracting a result although they do have a goal to take back to Camp Nou on January 17 thanks to Philippe Coutinho's potentially pivotal 85th-minute penalty.
"The tie is open after Coutinho's goal", Busquets told reporters after the 2-1 loss. "The team deserved that, above all for the second half".
And Arthur's arrival in the summer to replace Andres Iniesta means Coutinho can not even take up a more central position. "When you don't play and you aren't happy, you have to fight to change things".
The Argentine was left out of the squad along with usual strike partner Suarez and Ivan Rakitic, Gerard Pique and Jordi Alba, although regulars such as Ousmane Dembele, Arturo Vidal, Sergio Busquets and Coutinho all started the game.
"When it came to picking the side, I thought that was the best team we could pick for the game", Valverde said in a news conference when asked if he regretted his team selection. "It's a risk, maybe, but these are the risks we take".
Levante, who did enjoy a 5-4 La Liga win over Barcelona last season, were ahead after just four minutes through Cabaco as the defender rose highest to nod in Ruben Rochina's free-kick from six yards. The Brazilian, the club's record signing at €160 million, had endured a frustrating night before scoring the late penalty.
"Now he plays and Coutinho doesn't and it is the other way around". What the players have to do is work hard to revert the situation.
Valverde was blamed last season for Barca's shock Champions Leaue exit, the theory being that he failed to rest key players in the Copa del Rey and La Liga, both of which they won.
"But, come on, one or the other is almost always playing". There's tough competition here.
"Denis is in a different position to Munir [El Haddadi], because Denis can play for us in any match and he is always available".