Gayle's first-half double had put the visitors in complete control, before the Cherries fought back.
Benitez said: “Dwight was complaining about a little bit of tightness in his hamstrings, so we needed to make a substitution.
“The problem is that they were pushing and coming from the wide areas and making crosses.
“Ayoze was the striker, and we were trying to make sure that we had more control, but we were giving the ball away and they were pushing. Sometimes, you have to give credit to the other team."
Benitez admitted he was a bit shocked he wasn't talking about an away win, and in trying to explain the poor last 10 minutes, he said: “I don't think that we switch off, it was just a lack of concentration in a couple of situations where we could have done better.
“It is not easy to defend when they are attacking and attacking though, and it is hard to do everything perfect."