Fabregas confirmed his return to the Premier League after a three-year stay at Barcelona and also revealed former club Arsenal rejected the option to re-sign him.
But Del Bosque says the high-profile transfer will have little impact on his preparations for Spain's FIFA World Cup opener against the Netherlands on Friday.
"Everyone is in top condition," he said. "No transfer will affect the selection...everyone is very focused."
Spain were 3-0 losers to Brazil on their last trip to South America for the FIFA Confederations Cup last year, but Del Bosque is confident his side can rediscover the form that saw them win the 2010 World Cup.
"Our players are excited to play in Brazil, we were here last year but we look forward," he added.
"It's a veteran team, it's a mature team with people who are in shape, it's what they do, what they have done."
As well as the Netherlands, Spain come up against Chile and Australia in Group B.
