BERLIN, Sept 13 (Reuters) - Bayern Munich winger Arjen Robben could miss Saturday's clash against Mainz with a minor groin injury as the Bavarians seek to maintain their early season advantage over champions Borussia Dortmund.
Robben returned from international duty with an injury suffered during the warm up of the Netherlands' 2014 World Cup qualifier in Hungary earlier this week but medical checks in Munich on Wednesday revealed the problem was a minor one.
While he is not expected to be out for long, Bayern said they could be without their influential winger on Saturday.
The Bavarians lead the standings with maximum points from two games and after failing to win a single trophy last season, Bayern are eager to take control of the title race.
Coach Jupp Heynckes, however, may opt to leave Bundesliga record-signing Javi Martinez on the bench as he did in the previous game against Stuttgart.
"Obviously, from a footballing viewpoint he is a great asset for us but Javi still needs to work and fight his way into the team with performances," Heynckes said of the 40 million euro ($51.55 million) signing.
"Who plays depends on a lot of things. I would not want to decide this now."
Leaving the Spaniard on the bench has so far not stalled Bayern's charge to the top of the standings following their nine-goal spree in the opening league games.
"It was good to shoot out of the blocks like that," Heynckes told the club website (www.fcbayern.de). "The team is hungry and it has helped physical preparations."
Dortmund breathed a collective sigh of relief on Wednesday when medical checks confirmed in-form forward Marco Reus had not been seriously injured in Germany's 2-1 win over Austria a day earlier and would be fit to face Bayer Leverkusen.
Reus, the back-to-back champions' most expensive summer signing, is in fine form, having scored against Austria and also netting one goal in the league.
Dortmund are on four points from two games, two behind Bayern.
Fellow Champions League competitors Schalke, also on four points from two games, travel to promoted Greuther Fuerth.
$1 = 0.7759 euros Reporting by Karolos Grohmann; Editing by John O'Brien