Let me preface this by saying that this website is traditionally one of the least reliable sources of information available on the internet. I'd usually just laugh this off, except for the fact that this article specifically attributes a quote to an individual. That said, Miguel Angel Gil Marin (Atletico Madrid president) has been quoted with the following:
"Yesterday I received an offer of €45 million from Real Madrid for Aguero and I said no," Gil Marin told Spanish daily AS.
"This week, Chelsea offered us €60 million for 'Kun' and Godin and our answer was the same."I will not negotiate with Real Madrid or any other club for Aguero now or in the summer."
If this has any truth to it at all, between the wages that would be required and the transfer fee it appears Chelsea don't have any issues opening the checkbook at all. If this is the case, I wouldn't rule out another big move before the end of the window. It's also worth noting that Atletico were apparently asking for about 15 million euros for Godin alone, so they apparently don't seem to have much of a grasp of what their players are realistically worth.