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Juergen Klopp arrived at Liverpool in October armed with his megawatt smile and a renowned playing style: The so-called "Gegenpressen" approach that was the key to his success in Germany with Borussia Dortmund.

It involved attempting to win the ball back by defending vigorously from the front, closing down opponents regardless of where they are on the field, and playing at "full throttle" for the full 90 minutes. The result? Two Bundesliga titles and a place in the Champions League final in 2013.

Klopp has transferred the physically demanding approach to Anfield and the grueling English soccer calendar, but there's a growing worry that he is running Liverpool's players into the ground amid the team's hectic schedule of Premier League, Europa League and League Cup matches.

Liverpool currently has 11 players injured, six with hamstring problems. The team's injury woes intensified Thursday when playmaker Philippe Coutinho was ruled out until February by Klopp, who is without a senior center back for the third round of the FA Cup against Exeter on Friday — Liverpool's 31st game this season. Local media reported later Thursday that winger Jordon Ibe has joined the injury list, also with a hamstring problem, to make it 12 players sidelined.

Sunderland manager Sam Allardyce said Klopp has underestimated the ferocity of English soccer, adding the effects of a "high-tempo pressing game from the top end . has kicked in now."

Even former Liverpool manager Roy Evans has had his say, questioning the intensity of Klopp's training sessions.

Klopp sees it differently.

"We know about our situation, we know in most of the cases about the reasons," Klopp said Thursday, "and so it's often the situation where one injury at the wrong moment is a problem for the whole squad, because other players have to play too much.

"But that's all. You have to react to this. I knew about the intensity of the football here."

Dortmund had plenty of injuries in Klopp's seven-year reign, many toward the end of it but it is arguable whether that had anything to do with his playing style. There was little criticism of the approach at the time and Dortmund hasn't changed their style much this season under Thomas Tuchel.

So maybe it is just down happenstance.

"Sometimes you are just unlucky with injuries," Liverpool midfielder Adam Lallana said, "and we've had a lot of bad luck recently."

Klopp, who has already grumbled about the lack of a winter break in England, has often said there are misconceptions about his methods.

"The problem is now people speak about the intensity of my style — I didn't create a style, how could I? I am not a genius," he said Thursday. "We play only football and a team like Liverpool, with the ambitions the club have, we have to find a way to be successful.

"For this you need players, a little bit of luck with injuries but we haven't had too much of this ... It is completely normal, average running. Football is not all about more, it is more about thinking quicker and being quicker in the right position."

To combat the injury problems, Klopp has recalled 18-year-old forward Sheyi Ojo from his loan spell with second-tier club Wolverhampton Wanderers and is set to bring back Portugal under-21 defender Tiago Ilori from his loan stint at Aston Villa.