Sanchez was surprisingly left out of the starting XI as Wenger's side were beaten 3-1 at Anfield on Saturday.
The Chilean came on at half-time and set up Danny Welbeck to make it 2-1, but that was as good as it got for Arsenal.
Explaining his decision to leave Sanchez out and start Olivier Giroud and Welbeck, Wenger said he wanted more of an aerial presence.
"The thinking was that we had to go more direct and I wanted to play two players strong in the air because we decided to go more direct," the Frenchman said.
"After that [it was] to bring Alexis Sanchez on in the second half, but of course I believe in the second half it was easier for the strikers and you could see a different performance from Giroud and Welbeck because we dominated much more of the midfield.
"Everybody will come to the same conclusion but I am strong enough and lucid enough to analyse the impact.
"I don't deny that Alexis Sanchez is a great player, I bought him and I always played him and I think he has developed well with us.
"A decision like that is not easy to make but you have to stand up for it."
“We’re going with Giroud and Welbeck up front because we will need to be a bit more direct and strong in the air.” pic.twitter.com/NbSGcLlnaj— Arsenal FC (@Arsenal) March 4, 2017
First-half goals from Roberto Firmino and Sadio Mane put Liverpool in control before Georginio Wijnaldum sealed the result late on.
Wenger said he felt his team as a whole simply improved after the break.
"I don't think there's a need to go into any individual explanation. What was good in the second half was our collective performance," he said.
"What was not good in the first half was our collective performance. That's for me a much more rational explanation than all the rest."