Granted, there are a few questions surrounding the agreement. Agent Francois Gallardo is famous for making false claims regarding transfers. He was quoted by Spanish broadcaster "La Sexta" about the deal in place.
Other sources have backed up the claim, however.
Should the verbal agreement be inked, the Atletico Madrid striker would make his way to Stamford Bridge at season's end. He currently has 19 goals in 21 appearances in La Liga play, and he is widely recognized as one of the better strikers in the sport.
Madrid boss Diego Simeone is of the belief that Costa could soon be recognized as the game's all-around best striker. Simeone told Mundo Deportivo (via Andrew Wychrij of Goal.com):
"Diego Costa is not far from the Ballon d'Or. Things are not so bad for him."
Costa would effectively replace the exploits of Juan Mata—a fan favorite who was just sold to Manchester United as Jose Mourinho continues to search for answers prior to the transfer window's Jan. 31 deadline.
Chelsea's trio of Fernando Torres, Samuel Eto'o and Demba Ba on the attacking line have the potential to be dynamic, but they've only managed a combined 11 goals in 22 contests in Premier League play. It goes without saying that Costa would be a significant upgrade on the attack.
Once the deal goes down, the balance of power very well may shift closer to Chelsea's favor in the Premier League.