For the first time in his Barcelona career, Sergio Busquets is under scrutiny.
The midfield anchor has been the glue that has held the side together ever since Pep Guardiola, who had nurtured him in the club's B-team the year before, promoted him to the first team in September 2008, and the gangly youngster quickly usurped Yaya Toure as the first choice holding midfielder.
But cracks in his blemish-free image have emerged after making three clear and costly errors in the last two games. Busquets' dip in form has been muttered about quietly for a while, since the back end of last season when he appeared to lose his grip on midfield and the team briefly stuttered, suffering three straight defeats for the first time in 13 years. Now it can no longer be ignored.
Alarm bells started ringing in the Champions League last week when he was dispossessed by Borussia Monchengladbach's Mahmoud Dahoud in the middle of the pitch. Barca were cut in half by the German side's break, conceding the opening goal which was later overturned by Arda Turan and Gerard Pique.
They chimed even louder in a 4-3 defeat at Celta Vigo last Sunday, when Busquets was caught unawares by Marc-Andre ter Stegen's misplaced pass. Just three touches of the ball later, Celta Vigo took the lead. Clearly shaken by his errors and Celta's intensity, 11 minutes later he failed to head away a routine long ball over the top which found its way instead to Iago Aspas, who did the rest.
In the past, you would have been hard-pressed to find three big errors committed by Busquets over a season -- now there has been three in two matches. And although the last two games have exposed his vulnerability, the warning signs have been there from the start of the season. He looked tired in the 2-0 Spanish Super Cup first leg victory at Sevilla, was put to the test in the 1-0 win at Athletic Bilbao and was imprecise in the shock 2-1 defeat at home to Alaves.
Fans will hope these latest mishaps are merely blips by one of the team's most consistent performers and that he will soon return to the serene player who controls Barca's tempo. After all, it was only two weeks ago the 28-year-old's importance was made so glaringly obvious by Atletico Madrid. Barca never have it easy against Diego Simeone's dogged side, but they were in control at 1-0 up at half time, rarely giving the visitors a sniff.
Busquets, who had barely recovered from a fever before the game, had to go off early in the second half and minutes later, Atletico pulled level through Angel Correa, using a free kick to pounce on a Barca side that had fallen asleep without their midfield leader.
"Busquets' physical problems marked a turning point in the game," wrote former Barca striker Pichi Alonso in Sport.
"After "Busi's" departure, nothing was quite the same, demonstrating his importance to Barca's midfield."
Barca are now in a worrying situation where they lose grip in midfield when Busquets isn't on the pitch and are not much better when he is.
The midfielder took full responsibility for his weak performance after Sunday's debacle in Vigo, admirably agreeing to a postmatch interview.
"I'm one of the guilty parties, it obviously wasn't one of my best games," he said.
"You pay dearly for errors in midfield and I have to keep improving. Sometimes you mess up because you control the ball badly or you're not well-positioned. We're not robots nor machines."
Busquets used to be so consistent that he began to resemble a machine and successive Barca coaches -- from Guardiola to Tito Vilanova, Tata Martino to Luis Enrique -- have treated him like one. The midfielder played 44 of the club's 48 games in La Liga and the Champions League last season, and 43 of 51 the year before, accounting for three weeks out with an ankle injury.
The most obvious explanation for the relative decline is a lack of sharpness after little rest. The problem is partly Luis Enrique's making. The coach admitted last month: "The player that is going to rest least this season is Busquets, because of how specialised he is in his position."
While last summer's transfer policy was about signing backup for every position on the pitch -- bringing in a goalkeeper, full-back, centre-back, two attacking midfielders and a centre-forward -- Barca did not add cover in holding midfield. The one player with similar characteristics to Busquets, youngster Sergi Samper, was loaned out to Granada. The other player who could in theory give rest time to Busquets, Sergi Roberto, has been converted into the first choice right-back.
The seemingly obvious choice of Javier Mascherano, ostensibly signed by Guardiola in 2010 to lessen the burden on Busquets, has long been discarded. The Argentine, who continues to play in midfield for his country, is now almost exclusively employed at centre-back.
"Irreplaceable" is how Luis Enrique described Busquets last month.
Considering how he has played early in the season, another option would certainly come in handy.