Graeme Souness says that Chelsea would have won the Premier League last season if they had Diego Costa at their disposal.
The Blues finished last season's table in third position, but the Sky Sports pundit believes that they would have ended up with the title if they had the Spanish international in their squad.
"If Costa had been at Chelsea last season they would have won the league," Souness wrote in his Sky Sports column.
Costa arrived at Stamford Bridge this summer for £32 million and has made an immediate impact, scoring eight times in his first six games.
It was exactly what they didn't have in the previous campaign, where they struggled to find a goal in their strike-force.
The likes of Samuel Eto'o, Demba Ba and Fernando Torres have all proven their quality, but struggled in the Premier League last time around and Costa has been a serious upgrade.
Souness has also urged Jose Mourinho to be cautious with his new man, though.
The former manager has warned the Blues boss that playing him too regularly could mean that he loses his sharpness.
"The main question mark he has is how much time on the pitch to give to Diego Costa," he wrote. "The Chelsea manager is looking at the big picture, which is that Costa is so far ahead of the other strikers at the club that he needs to protect him."
"Because of that – and because of his fitness concerns - he will know that he needs to protect him."
Chelsea take on Sporting tonight in the Champions League and Souness feels that Costa should be risked in the game.
The Brazilian born hitman was rested against Schalke in their first match in the competition and Mourinho's side could only collect a point without him, meaning that their fixture tonight has added pressure on it.