The Argentina midfielder joined West Ham as a free agent this month after coming off contract at Real Betis in June.
Guido told AS: “The negotiation with West Ham took place practically in two days. Until that moment, I was in contact or had spoken with Betis, with the club. They also had problems being able to sign due to the salary limit, as happens to many teams in Spain.
"Until that moment I didn't know what could happen, and I also had it in my head to be able to continue.
I didn't know what was going to end up happening. The truth is that this (the signing for West Ham) happened very quickly. Until two days before traveling (to London) I didn't know what was going to happen, that's the reality.
"These are football things, we have to look forward and keep working."