Borussia Dortmund and United States men's national team winger Gio Reyna has had a further setback to his recovery from a groin injury.

Reyna strained his groin while training with the USMNT last month, missing friendlies against Canada and New Zealand.

He has now incurred what Dortmund called a "setback" in his recovery. The club didn't give further details of a timeline for his return.

It's the latest in a long series of injury difficulties for Reyna, whose only playing time for Dortmund this season was a brief substitute appearance in his team's first Bundesliga game of the season in August.

Meanwhile, Reyna's Borussia Dortmund teammate, forward Karim Adeyemi, is set to miss more than a month with a muscle injury after scoring three goals in his team's 7-1 win over Celtic.

The injury to Adeyemi is more serious than first feared and comes just as his first-half hat trick Tuesday had Dortmund coach Nuri Şahin hoping he could consistently be one of the Champions League runner-up's top players.

Adeyemi was taken off early in the second half of the Celtic game with what seemed to be a thigh problem, but he had indicated that it didn't seem that serious. Now Şahin says Adeyemi is unlikely to return until after an international break in mid-November.

That would mean the 22-year-old forward misses a Champions League game at Real Madrid on Oct. 22 in a rematch of last season's final and a challenging Bundesliga game against RB Leipzig on Nov. 2.

Sahin also said 18-year-old forward Julien Duranville, who replaced Adeyemi off the bench against Celtic, would be out for a similar amount of time with a thigh injury.

Dortmund's next game is Saturday at Union Berlin in the Bundesliga.