Boris Becker was a legend on the tennis court, unfortunatly when it comes to investing, he appears to have shared an advisor with Johnny Depp.

According to claims in the German media, Boris Becker may have lost his roughly €100 million fortune in part because of questionable investments in the Nigerian oil industry. Ever since the 49-year-old former tennis star was declared bankrupt in a London court last month, there has been rampant speculation over how he managed to squander a personal fortune estimated at roughly €100 million.

Now, according to Germany’s Spiegel, Becker’s business dealings went far deeper than celebrity endorsements and media appearances. The magazine claims he made investments in the Nigerian oil and gas industry, and at one point considered a single investment of more than $10m (£7.6m).

It also alleges he had extensive links outside the world of tennis that ranged from African leaders to Laxmi Mittal, the Indian steel billionaire, and was seen as some one who could facilitate business deals.

The claims centre on documents Spiegel says it was shown by Football Leaks, a whistleblowing website. They documents include alleged internal emails from Doyen Global, a sports management agency which represented Becker for a brief period starting in late 2013, which reportedly show that Becker Private Office, a company controlled by Becker, held extensive shares in the Nigerian oil and gas business, Spiegel claims.

The magazine claims it has seen details of a single investment of “more than $10m” in Nigerian oil prepared for Becker by Forbes & Manhattan, a Canadian investment bank and a former associate of the tennis player. It notes that it was not clear whether Becker went through with the investment, or whether it was successful, although judging by his recent bankruptcy, the odds are not good.

As the Telegraph adds, Becker’s association with Doyen was publicly presented as an opportunity for the company to expand its operations in the world of tennis. But the allegedly email leaks note that he had met recently with Mittal and John Mahama, the Ghanaian president at the time, and describe him as “some one who can open doors for us in certain circles”.

Meanwhile, during bankruptcy proceedings in London last month, John Briggs, Becker’s laywer, told the court: “He is not a sophisticated individual when it comes to finances.” His bank account seems to agree.