Jupp Heynckes says Thiago Alcantara suffered a serious muscular injury during Bayern Munich's 2-1 win over Anderlecht in the Champions League on Wednesday, but Arjen Robben may have escaped more lightly.
Thiago was replaced just before half-time, with Javi Martinez coming on for the midfielder as Bayern shrugged off a slow start to pick up all three points.
Robben, meanwhile, was withdrawn three minutes into the second half.
Speaking after the match, Heynckes revealed the club faced an anxious wait to discover the severity of the Spain star's problem.
"Thiago suffered a serious muscular injury," he told Sky.
Of the veteran Dutchman, Heynckes added: "Robben said, he thinks it's not too bad. We have to wait for the diagnosis."
Heynckes was not completely satisfied with his side despite the victory, a result that keeps them second in Group B, three points behind Paris Saint-Germain, ahead of a clash with Unai Emery's side at the Allianz Arena next month.
Anderlecht had the better of the chances in the first half but the visitors won it after the break thanks to goals from Robert Lewandowski and Corentin Tolisso.
However, Heynckes felt Bayern were complacent against an Anderlecht side yet to pick up a point in the group stages.
"We played very badly in the first half and gave away two or three big chances," he added.
"Of course you need to be direct about that with the team. We went into the game thinking it would be an easy game because our opponents didn't have a point in the group. We gave the ball away far too often and they had too much space."
|James leaving Madrid was the best thing, says father|
|He´s looking good – Zidane thrilled with Ronaldo|
|It needs to take 30 seconds – Matic wants quicker VAR|
|Team LeBron edges Team Stephen in thrilling All-Star Game|
|McIlroy sees progress despite failing to contend at Riviera|
|Silver supports NBA players speaking out on social issues|
|Mickelson ready for Masters after third straight top-six finish|
|Gattuso: My job is to be the players´ nightmare until season´s end|
|I wasn´t good enough – Guardiola reveals Wigan rejection|
|Dillon reigns supreme with overtime win at Daytona 500|
|Bubba Watson ends drought with third Genesis Open title|
|Brazilian derby between Vitoria and Bahia abandoned after red-card frenzy|
|Anderson ends barren spell with New York Open triumph|
|It was crazy, but I like that - Zidane revels in eight-goal Betis thriller|
|Asensio credits Zidane for Madrid´s thrilling Betis comeback|
|Zidane hopeful over Marcelo hamstring injury|
|Overton replaces injured Plunkett for Blacks Caps ODI series|
|Bonaventura claims Milan can catch Inter|
|Bravo for Claudio! Guardiola to pick keeper at Wembley|
|Mourinho hoping for reinforcements at Sevilla|
|´Quick-healer´ Groves hopeful over shoulder injury|
|Real Madrid become first side to score 6,000 goals in LaLiga|
|Real Betis 3 Real Madrid 5: Asensio at the double in LaLiga classic|
|AC Milan 1 Sampdoria 0: Bonaventura makes it 10 unbeaten for Rossoneri|
|Schurrle excited to finally link up with Reus and Gotze|
|Fit-again Hughes included in England squad|
|New number one Federer revels in ´unbelievable´ week|
|Real Madrid defender Marcelo suffers hamstring injury|
|Costa fumes referees ´want to give me a card´, but Simeone plays down penalty row|
|Thiem regains Argentina Open title|
|Stoger makes Dortmund history with Gladbach win|
|Championship Review: Leeds fight back for point, Norwich & Ipswich share derby spoils|
|Racing beat La Rochelle to go second, Castres edge out Bordeaux|
|Borussia Monchengladbach 0 Borussia Dortmund 1: Burki unbeatable as Reus returns to haunt Foals|
|FA Cup ´magic´ no surprise to Pochettino after Rochdale thriller|
|Rochdale hero Davies: This is every kid´s dream|
|Atletico Madrid will not stop in pursuit of Barcelona, promises Gameiro|
|Banks boot pays dividends for Treviso|
|Lucky 13 and second successive title for Kvitova after Muguruza classic|
|´Wrong image´ to blame for VAR confusion in Manchester United´s FA Cup win|
|Rochdale 2 Tottenham 2: Davies denies Kane in FA Cup classic|
|Rieder stretchered off as Wasps extend Chiefs´ slump|
|Atletico Madrid 2 Athletic Bilbao 0: Gameiro and Costa settle cagey clash|
|NHL commissioner Bettman condemns ´reprehensible´ Smith-Pelly abuse|
|Visser, Scott and Nel among six recalled by Scotland|
|Bhuvneshwar and Dhawan inspire India´s Wanderers win|
|Napoli set club record with another Serie A win|
|Froome disappoints in time trial as Wellens wins Ruta del Sol|
|Napoli 1 SPAL 0: Allan sends hosts top of Serie A again|
|Federer makes short work of disappointing Dimitrov|
|Allegri allays Higuain injury fears|
|Blackhawks fans ejected after racist heckling of Capitals´ Smith-Pelly|
|Allegri convinced Juve can get past Spurs|
|Sri Lanka sweep series after dominating Bangladesh|
|Everton fear ´long-term´ injury for Mangala|
|If it isn´t Madrid, it´s Paris - Hazard tires of speculation|
|Luiten claims Oman Open title|
|Torino 0 Juventus 1: Champions win derby but lose Higuain|
|Neymar exit made Barcelona stronger - Ter Stegen|
|Remove T20 cricket from international schedule - Bayliss|
|Injured Higuain forced off against Torino|
|Jesus confident of returning strong after knee injury|
|DeGale launches Twitter attack on beaten Eubank Jr|
|We had to change hotels – Ovrebo recalls fury after 2009 Chelsea-Barcelona semi-final|
|Spalletti: Inter board will decide my future|
|Munro blitz helps Black Caps progress despite defeat|
|Fabregas still wary of timeless Iniesta|
|Liverpool´s 30-goal hero Salah: There´s more to come|
|Valverde: Coutinho dropped for the good of Barcelona|
|Garcia floors Rios for ninth-round TKO|