The likes of Isco and Saul Niguez were left out for the European Championship, at which Spain will face the Czech Republic, Turkey and Croatia in Group D.
Del Bosque said he understood players would be disappointed, but he had no question marks over his selection.
"I really think all of the them are the same, knowing how difficult it is to be out ahead of a major tournament like the European Championship," he said.
"Saul, Isco, Mario [Gaspar], [Santi] Cazorla, [Juan] Mata … we do have many players who haven't come.
"I don't regret just one comparing the others."
Arsenal defender Hector Bellerin was included after Dani Carvajal was ruled out of the tournament due to a hip injury.
Del Bosque said he was happy to back the 21-year-old Bellerin, who has just one Spain cap to his name.
"I admit we were doubtful the day we made the list in terms of right-back," he said.
"We chose Carvajal and Juanfran but Mario also deserved to be here.
"Anyway, this time we bet for Bellerin who is a guy for the future but also for the present as he is a player of Arsenal."