By Karolos Grohmann
EVIAN, France (Reuters) - Germany's defense will be put to the test in their opening Euro 2016 group match against Ukraine in Lille on Sunday with major questions still to be answered about the world champions' new-look rearguard.
Coach Joachim Loew's team will be without key central defender Mats Hummels, still recovering from a muscle injury, as they kick off their Group C campaign.
Hummels' replacement Antonio Ruediger was ruled out with torn cruciate knee ligaments this week.
Holding midfielder and captain Bastian Schweinsteiger, still working on his comeback from injury, is also absent, further complicating Loew's defensive conundrum.
Benedikt Hoewedes and Jerome Boateng are the two likely central defenders but both had a long injury break late in the season and are in desperate need of match practice.
Jonathan Tah, the 20-year-old who was only called up this week following Ruediger's injury, is expected to be on the bench.
Toni Kroos, who will shoulder the biggest responsibility of connecting Germany's defensive and attacking game, is brimming with confidence following his Champions League win with Real Madrid.
Assistant coach Thomas Schneider sounded confident on Friday that the team would quickly find their cohesion at the back.
"In the last few matches we thought a lot about our defensive operation and we came up with a few things, including for defensive set pieces," he said.
"We have worked on that in training and everyone knows their job."
Ukraine, while outsiders, are certain to test the Germans' new-look defense with quick wingers Andriy Yarmolenko and Yevhen Konoplyanka capable of inflicting severe damage.
It will be up to Loew's full backs to neutralize that threat but they must also break down a steely Ukraine defense.
The Germans, eyeing their fourth Euro triumph but first since 1996, have never lost an opening match at the European Championship and are aware a slip-up could prove costly.
"The first game is extremely important and it will determine our run in this tournament," attacking midfielder Julian Draxler said.
Ukraine managed to keep six clean sheets in 10 qualifiers with coach Mykhailo Fomenko having taken over after the co-hosts' disappointing Euro 2012 campaign.
They then came out on top against Slovenia in a playoff last year, with the 67-year-old having moulded them into an efficient unit.
(Editing by Ian Chadband)