Last season, Marcos Alonso was named in the PFA Team of the Year. Now, he is no longer sure of being named in the Chelsea team.
In that sense, the left-back's fall has been as rapid and remarkable as his rise.
Alonso's £23 million ($30m) signing from Fiorentina in the summer of 2016 raised eyebrows as he was coming off the back of an underwhelming loan spell at Sunderland.
However, after Chelsea switched to a 3-5-2 under Antonio Conte, the Spaniard excelled as a wing-back, playing a pivotal role in the club's Premier League title success and run to the FA Cup final.
Alonso remained an integral member of the Italian's squad last season, as the Blues won the FA Cup, and followed in the footsteps of his father and grandfather by breaking into the Spain squad, at the age of 27.
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His dynamic displays down the left flank sparked talk of a return to his homeland - Barcelona, Real Madrid and Atletico Madrid were all linked with his services - but neither Chelsea nor new manager Maurizio Sarri had any intention of selling Alonso, who signed a new five-year contract in October.
Since then, though, Alonso's stock has fallen dramatically.
Sarri's arrival has forced everyone at Chelsea to adapt to a very different brand of football to Conte's. Some have fared better than others.
Like N'Golo Kante, Alonso seems to be suffering the effects of being moved from his preferred position.
Sarri's rigid 4-3-3 formation has seen Alonso deployed as a conventional left-back. The positional change has meant fewer opportunities to get forward and being asked to focus far more on his defensive responsibilities.
There were no problems initially.
Alonso was one of Sarri's key men as Chelsea kicked off their 2018-19 campaign with an 18-game unbeaten run, with the Tuscan describing the Madrid native as "maybe the best left-back in the world" after a run of four assists in the first four Premier League outings of the season.
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However, Sarri did caveat his comments by asking for improvements in the "defensive phase" from Alonso.
The suspicion that Alonso hadn't quite got the balance right intensified after Chelsea suffered their first defeat of the season, a humbling 3-1 loss at Tottenham a month after he had renewed his contract.
At Wembley, Alonso was among those who had "stopped playing football", as Sarri put it, and since then, a host of teams, including Wolves, Manchester United, Manchester City and Arsenal, have looked to exploit the left-back's desire to get forward.
Most infamously, Alonso was at fault for the first goal in a 6-0 drubbing at the Etihad Stadium that cast serious doubt not only over his suitability to the role of a conventional left-back, but also Sarri's future at Chelsea.
Sarri is not one to rotate, even when a player is struggling, so it is telling that Alonso has increasingly had to share his once undisputed starting berth with former understudy Emerson Palmieri.
No other 'reserve' has managed to take the place of one of Sarri's 'untouchables' yet Emerson is giving it a good go.
Indeed, it seems there is very little to choose between the pair right now, with Sarri having already admitted that sometimes he only picks Alonso as he is the taller of the two, thus allowing him to compensate for a lack of height elsewhere in the Chelsea team.
"Of course. Emerson is a good option," the former Napoli boss admitted. "But I have to consider, also, some details.
"For example, without Alonso, we could have problems [defensively] at set-pieces. So, I have to consider everything."
Sarri added, though, that Alonso's form is also a major factor in his thinking and the reason why the Real academy product has been omitted from a lot of squads of late.
"You have to accept that a player cannot stay at the top of his physical condition and mental condition for 11 months," he reasoned. "So, we were lucky because, in that recent period, we had a very good moment for Emerson.
"And now I think Marcos started to return to his best. But, in 11 months, you have to accept one or two months of difficulty.”
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Emerson himself hasn't been without his shaky moments. He was, after all, involved in the shock 4-0 defeat away to Bournemouth.
Still, the statistics underline why Sarri feels Emerson is just as good an option at left-back right now.
Even though Alonso (34) has played 15 more games than Emerson (19) this season, the Italy international has actually completed more dribbles (39) than his rival (22), while he also boasts a better pass completion rate (90.9 per cent to 85.5%).
Alonso is, as Sarri has pointed out, superior in the air, winning, on average, 1.8 aerials per game (Emerson's tally is 0.9), but he has only been directly involved in three more goals than Emerson (6 to 3) despite his far greater game time.
Emerson is also proving the more accurate crosser of the ball, although Alonso is averaging more successful tackles. However, that could be explained by the fact that Alonso is having to make more challenges simply because he is being targeted by opponents.
Of course, Alonso's issues at left-back need to be viewed in a broader context, with Chelsea suffering a lack of balance in midfield, looking vulnerable in the centre of defence and not pressing adequately up front. In that sense, he is not the only one struggling.
However, the fact remains that Emerson is putting him under intense pressure right now. The onus is on Alonso to respond and show just why he was voted the best left-back in the PFA Team of the Year last season.