Mats Hummels would welcome Mario Gotze with open arms if the Bayern Munich attacker decided to return to Borussia Dortmund.
The 23-year-old left BVB for Bayern in July 2013 for a transfer fee of EUR37 million, but he has been unable to live up to the high expectations at the Allianz Arena.
Gotze has only started in five Bundesliga matches this season and was recently linked with a return to Dortmund, with defender Hummels feeling his former team-mate would be a shrewd addition for Thomas Tuchel's side.
"I don't know how realistic a return to Dortmund is for Mario," Hummels told ZDF.
"But he is a player with the potential to become a world-class player. We had some great times together, both at Dortmund and with the national team.
"We are all suffering with him when we see things are not going his way due to bad luck. I would really like to see him back to his best.
"It would be great if he makes the decision that Dortmund is the place to achieve that. It would be a huge boost of quality."
Hummels also revealed he is yet to decide on his own future at BVB, with his current contract due to expire in 2017.
He added: "I am still undecided on my future. There are a lot of things I would like to do.
"One of those things is to stay at Dortmund a bit longer and build on what we are doing right now.
"But I also realise that it would be a long-term decision if I sign a new deal. It could be my last contract. I am not in my early 20s."