Chelsea manager Jose Mourinho
Mourinho keen to find a replacement for Ashley ColeReuters

Chelsea have reportedly tabled an improved offer of £15 million for Atletico Madrid defender Filipe Luis after seeing their earlier bid rejected by the Spanish club.

After successfully wrapping up Diego Costa's deal for a reported £32 million, the Blues had tabled a £12 million bid to get Atletico Madrid's Luis as well. However, according to the Times, the Spanish Champions rejected the Blues' offer.

Still Chelsea boss Jose Mourinho is adamant on getting the 28-year-old as a replacement for Ashley Cole, who has joined Roma on a free transfer.

Although Southampton's Luke Shaw was reportedly the "Special One's" initial target, he was forced to look at alternative options following his transfer to Manchester United for a reported fee of £30 million.

Chelsea were believed to be confident of getting Luis' signature for a transfer fee in the region of £10 to £12 million, but it seems like Atletico are unwilling to let their defender go for a cheap price.

Though the La Liga champions are believed to be demanding a transfer fee of £19 million (the amount thought to be in the full back's buy-out clause), Chelsea are certain they can wrap the deal for £15 million.

However, if the Blues fail to convince Atletico to let go off their defender, the West London side do have a couple of alternatives - Sporting Lisbon's Marcos Rojo and Sevilla's Alberto Moreno, who are both rated at £15 million.

Meanwhile Tottenham Hotspur are reportedly looking to make a £20 million bid for Chelsea striker Romelu Lukaku, according to the Metro.

The 21-year-old striker has recently publically stated that he wants to leave Stamford Bridge for good after getting tired being loaned out every season.

The Belgian international, who was transferred from Anderlecht to Chelsea for a reported transfer fee of £17 million in the summer of 2011, has hardly made any appearances for the Blues, spending the last two seasons on loan at West Bromwich Albion (2012/13) and Everton (2013/14)

Despite finding success with both the clubs, scoring 17 and 15 Premier League goals at West Brom and Everton respectively, he was unable to break into Chelsea's first team.

Now with the arrival of Costa, Lukaku knows he will not be getting a chance at Stamford Bridge, which is why he is keen to leave Chelsea.

And Tottenham are trying to "strike while the iron is hot" by reportedly making a £20 million bid for the estranged striker.

Although Lukaku has stated his desire to join a Champions League club, he may be willing to settle for the Euro League as it is believed that the Spurs are the only ones who have come up with a tempting offer.