Philipp Lahm had injured his ankle while playing for Bayern Munich in the German Cup final of 2013-14.
Germany host Armenia on Friday in their final World Cup warm-up match before Brazil 2014 with stars Philipp Lahm and Bastian Schweinsteiger to return, while goalkeeper Manuel Neuer misses out.
Right-back Lahm (ankle) and Neuer (shoulder) have both been unable to play since picking up injuries playing for Bayern Munich in the German Cup final three weeks ago.
Both Germany captain Lahm and midfielder Schweinsteiger, who has had tendinitis of the knee, are expected to take some part in the Mainz match, but Roman Weidenfeller will deputise for Neuer.
"Both Philipp and Bastian have trained without problems and I assume they will play, but I don't know yet for how long," Germany coach Joachim Loew said on Thursday.
"I have spoken with Manuel Neuer and he won't play against Armenia, but there is no problem with him being ready for our first (World Cup) game against Portugal (on June 16)."
After Germany were held to a 2-2 draw by Cameroon last Sunday in Moenchengladbach, Loew wants improvements in their passing game.
Having drawn their other recent friendly against Poland, Loew wants a confidence-boosting win before flying to their World Cup base in Porto Seguro, via Salvador, from Frankfurt on Saturday.
"We want to win with a good performance, so we can leave Germany with a smile and to get in a good rhythm for the World Cup," said Loew.
Loew admitted his chief play-maker Mesut Ozil did not have "one of his best days" against Cameroon and pressure is on the Arsenal star to perform.
"I am bit surprised by the (negative) reaction against Ozil, perhaps his performance wasn't the best, but when you talk to him you see how confident he is," said Loew.
"He'll give his all for the team, we're convinced of his skills and that he'll be ready for our group matches."
Ozil, who joined Arsenal from Real Madrid at the start of the season, has suffered a drop in form recently having suffered a hamstring injury.
- Ozil 'looks lost' -
Ex-Germany captain Michael Ballack says Ozil "looks lost" on occasion and is concerned whether the 25-year-old will recapture his form before the World Cup.
"In the last few months, since his move to Arsenal, he has not been the same player, in terms of his confidence, that we used to see in the national team," Ballack told British tabloid the Daily Mirror.
"It's difficult to say where his head is going to be at the World Cup."
With only one recognised striker in the squad, Loew has said he has other options to veteran Miroslav Klose, who turns 36 on Monday.
"Lukas Podolski, Marco Reus, Mario Goetze can all play up front, so we have options if we need them," said Loew.
Armenia lost 3-1 to Algeria in a friendly in Switzerland last Saturday but beat the United Arab Emirates 4-3 last week with Dortmund playmaker Henrikh Mkhitaryan scoring twice.
Germany, ranked second in the world, have posted big wins over the Armenians, who are ranked 38th, in their two previous meetings -- a 5-1 win in 1996 during a World Cup qualifier was followed by a 4-0 win in 1997.
Loew will be looking for his 71st win in his 105th international match in charge.