The defender pulled up holding his hamstring as Aspas found himself in space to cross and set up Maxi Gomez, and Valverde has vented his frustration at the result.
"We had the chance to go 3-1 and then that situation [that led to injury] cost us two points, as normally you have an extra defender," he told Marca.
"That move saw the culmination of several pieces of misfortune with the equaliser and the injury. That was the way the game was and Celta are a good side and had the ability to equalise.
"To lose Samuel is a big blow for us as he has been playing well. After their goal we became more incisive and got the equaliser. After that we started to dominate and in the second half we got the second goal but then came that unfortunate move which cost us."
Barcelona, who remain unbeaten in La Liga this term, are now eight points ahead of second-placed Valencia.