Switzerland coach Ottmar Hitzfeld has said Borussia Dortmund and Bayern Munich are among the four favorites to win the Champions League.
Hitzfeld, who lifted the trophy with Dortmund in 1997 and Bayern in 2001, praised Borussia for their "sensational" performances in the group stages and said their coach Jurgen Klopp could emulate his achievement.
In his column for kicker, Hitzfeld praised German clubs for their successes in the Champions League so far and predicted that a golden age was ahead for football in Germany.
"Clubs and national team profit from youth schemes," Hitzfeld wrote. "Bayern have Muller, Kroos and Badstuber. Dortmund have Gotze, Reus and Hummels, and Schalke have Holtby, Draxler and Matip, to name a few.
"The German stadiums are filled. Therefore, the good record of German clubs is logical."
He said Dortmund had produced an "incredible performance" to win a group containing Manchester City, Real Madrid and Ajax, and added: "Dortmund were enjoyable, with their creative, disciplined and hard-running style at the highest level.
"If Barcelona, Real and Bayern are regarded as the favourites, after this group stage you have to name Dortmund as well."
But Hitzfeld warned that Schalke's progress could be hindered by uncertainty over the futures of key players such as Holtby, who has been linked with a move to the Premier League, and striker Klaas-Jan Huntelaar.
"The discussions surrounding Huntelaar and Hotlby put a strain on club, squad and fans," he wrote.