Sebastian Kehl says Shinji Kagawa would be welcomed back to Borussia Dortmund with open arms.
Douglas has described his arrival at Barcelona as the pinnacle of his career ahead of their visit to Villarreal on Sunday.
Roberto Martinez has insisted he is fully focused on Wigan's future, despite speculation linking him with a move elsewhere.
After securing the Latics' eighth straight season in the Premier League, the Spaniard has called on fans to celebrate during the home game against Wolves on Sunday.
And Martinez, who has been linked with Liverpool and West Brom, is also committed to ensuring the club continues to grow for the next decade.
He said: "All I am concerned about is that the football club is still growing and continues to do so for the next 10 years.
"I am the manager of an incredible football club and any talk of other clubs - especially when there is nothing on the table - is extremely disrespectful.
"There has been talk in the press, but I have another three years on my contract and I don't see it as an issue at all.
"If one day that's a decision that needs to be made, then I would look at it, but it's not the case at the moment."
Wigan boast the second lowest average attendance in the top flight, but Martinez wants fans to come in their droves to the DW Stadium on Sunday to celebrate the club's achievement.
He wants this to include a minute's applause after eight minutes in recognition of the number of top-flight seasons the club have secured
He continued: "We'll obviously be trying to win the football match, but it's just as important that there is a festive atmosphere at the DW Stadium.
"We need to realise that eight seasons in the Premier League is an incredible achievement - and that goes for all the players and managers who have contributed to that.
"I want the stadium to reflect the fact we have achieved something and it will be a proud day for us all."