The Blues defender has developed into one of the best left-backs around and it is no surprise to see him attracting interest from his homeland
He may not have Eden Hazard's trickery or Willian's pace but Marcos Alonso's ability as a footballer, and importance to Chelsea, cannot be understated.
His progess at Stamford Bridge has seen admiring glances arrive from Real Madrid and Atletico Madrid, while Barcelona have also considered him as an option to play at centre-back.
Their interest comes two years after he signed for the Blues, having arrived from Fiorentina in a £23 million ($30m) deal that left many scratching their heads as to why a Premier League title contender would be bringing in a player who had only been on loan at Sunderland a few years prior.
After leaving Real Madrid, where he'd primarily been playing for their 'B' side, Alonso spent three seasons at Bolton Wanderers before the aforementioned loan spell on Wearside. It had seemed, back then, that his career wasn't going anywhere fast.
Since then, though, he has starred for Fiorentina in Serie A to earn his big move to Chelsea, where his top-level performances have seen him receive rave reviews as well as call-ups to the Spain national team set-up.
Should interest from La Liga return in the January window, Maurizio Sarri's side may well be pressed into offering a new deal to Alonso - but it certainly wouldn't be undeserved.
These are fruitful times for a player who has had to be patient to reach the top, with Alonso having only won his first trophy - the Premier League title no less - in 2017.
Michael Laudrup's son Andreas played with Alonso at Real Madrid Castilla and built up a friendship with the left-back, with the Blues defender having communicated with the Dane in English in what was a difficult Spanish-speaking environment for new players at the club.
And Laudrup believes Alonso has been quietly making smart decisions throughout his career and, having become a football agent having retired early from the professional game due to injury, he now uses the Spaniard as an example to the players he manages.
"We always travelled together to training," Laurdrup told Goal. "The thing I remember from Real Madrid was that I came to the club without speaking Spanish.
"It was hard to understand the instructions in training and in the games without being able to understand the language but thankfully a couple of team-mates like Marcos could speak English.
"They could translate a little bit for me. For me, there’s no words that can explain how impressed I am about his career. When I played with him at Real Madrid he was good but now he is one of the players I tell my players to look at.
"Look at the steps he made before coming to Chelsea and how he always made the right decisions. That’s amazing, he is now playing at Chelsea, won the league and now he has made his debut for Spain’s national team. That’s an amazing career."
Having flourished in former manager Antonio Conte's preferred 3-5-2 and 3-4-3 systems, Alonso has looked largely impressive under new boss Sarri and the switch to a back four.