Mats Hummels says Bayern Munich won't win the Champions League this season unless they "get lucky."
Hummels, a former captain of Borussia Dortmund, was a member of Jurgen Klopp's side that lost the 2013 Champions League to Bayern 2-1 at Wembley.
And, in an interview with Nitro, Hummels said that although Bayern's squad had the "potential" to lift European football's top club trophy if they can progress past Besiktas in the round-of-16, the defender believes winning the title will be a step too far this season.
"The way we have played so far, I don't believe it is possible to win," he said. "Of course, we could get lucky, but I believe we will have to improve in a lot of areas.
"We must continue to improve if we are to have a chance in Europe, as we are nowhere near where we want to be."
Hummels also believes the Bundesliga is lagging behind other top European leagues. Bayern are leading the Bundesliga by 16 points and heading for their sixth league title in succession.
Hummels admitted that from a "competitive aspect" Bayern's massive advantage at the top leaves "an unsavoury taste" and added that the German league "definitely lacked a second or third side that can consistently pick up points" -- with last season's champions winning by 15 points.
"Other leagues are clearly ahead," he said. "The Spanish and the English leagues are the strongest. We have to be careful not to slip behind other leagues."