Alonso has been sidelined from Frank Lampard’s first-team plans and has not featured in Chelsea’s Premier League squad since the end of September, when he was substituted at half-time during the Blues’ 3-3 draw with West Brom.
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Alonso, who was born in Madrid, spent 11 years at rivals Real before moving to Bolton Wanderers in 2010. He is contracted at Stamford Bridge until 2023.
Atletico currently lead La Liga and Diego Simeone has used both Renan Lodi and Yannick Carrasco as left-sided full-backs this season. Simeone has often employed a five-at-the-back formation and Alonso is considered well-suited to a wing-back role.
Both Alonso and Emerson were previously of long-term interest to Inter Milan but, while the latter has attracted interest from both the Premier League and abroad, he is expected to remain at Chelsea until at least the summer in the event of Alonso’s departure.
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