The Dutch midfielder could make his debut against Levante today.
Guardiola said: "We knew that the market doesn't open until the 3rd (of January). It's a shame, because he (Afellay) would have been useful to cover for missing people.
"But it is good that Afellay has come, he's been well received. Now the urgent thing for him now to learn the language."
"The first thing that struck us is what a good player he is and the different things he can offer. He rarely loses the ball, he can play inside, he uses space well, he can play on both wings, he can shoot with both feet and he is very willing.
"He has all the time in the world and needs to be patient. He needs to integrate and when we can, we'll give him time on the pitch."