Coach Joachim Loew has a wealth of midfield talent but far fewer options in defence with a final decision on his centre backs still pending as Germany bid for a fourth European crown in a tough group that also includes Netherlands and Denmark.
While Holger Badstuber looks set to start at the heart of the German backline, speculation over his partner continues.
Fellow Bayern Munich defender Jerome Boateng is likely to switch to the right, a position he is uncomfortable with, to make way for central defender Per Mertesacker. Lars Bender could also an option at right back, Loew said on Thursday.
The experienced Mertesacker, however, has hardly played since an ankle injury in February and looked completely out of place in the 5-3 friendly defeat by Switzerland in late May.
Captain Philipp Lahm will shift from his usual slot on the right to left back which is not his preferred position.
"We will need to talk a lot on the pitch and to support each other," Mertesacker said. "I am experienced in understanding what the team needs."
"We have angered him (Cristiano Ronaldo) a few times in the past and we must do it again. What we should not do is give him too many one-on-one situations."
The defence will rely on holding midfielders Sami Khedira and Bastian Schweinsteiger to get early tackles in on Ronaldo, though 'Schweini' is far from his best after nursing a nagging thigh problem for two weeks in a season sprinkled with injuries.
"We have to go to him (Ronaldo) early and take away any space he has," said his club team mate Khedira.
"Basically, we need to spoil his enjoyment. He is Portuguese and the Portuguese do not function that well when they do not enjoy themselves.
"I have never seen anyone else who has Cristiano's talent and confidence. He can just do everything. I think you can never completely shut out a player like Ronaldo."
For Portugal, the key to success against Germany will be how Ronaldo plays his part in his team's collective effort.
The forward has said Portugal's aim is to win the tournament after coming agonisingly close as hosts in 2004 when they were upset by outsiders Greece in the Lisbon final.
The Portuguese, however, have not beenn impressive in their last two friendlies, drawing 0-0 against lowly Macedonia and losing 3-1 to Turkey on June 2.
"We want to go as far as possible, and our first objective is the quarter-finals, that is what is set out at the moment," said Portugal coach Paulo Bento.
Factbox: Germany v Portugal
Facts and figures ahead of Saturday's Euro 2012 Group B match between Germany and Portugal at the Arena Lviv in Ukraine
* Germany have reason to be wary of Portugal who beat them 3-0 when they met in the Euro 2000 finals in Rotterdam. Germany finished bottom of their group then. However, the Germans avenged that defeat at the last tournament, beating the Portuguese 3-2 in Basel in 2008.
* Portugal were the first team to beat Germany in a World Cup qualifier when they won 1-0 in Stuttgart in 1985, ending an unbroken run of 36 such games without defeat. Incredibly, the Germans have lost just one World Cup qualifier since, 5-1 to England in Munich in 2001.
* The last meeting between the two teams was in the third place match at the 2006 World Cup. Germany won 3-1 in Stuttgart.
* Germany, who won all 10 matches in their qualifying group, have found the net in each of their last 16 internationals and have scored three goals or more in nine of those. The last time they failed to score was in a 0-0 draw away to Sweden in November 2010.
* Since winning the title in 1996, Germany have lost more matches at Euro finals than they have won. They have lost five and won only four out of 12.
* Portugal have advanced beyond the group stage at each of the last four Euro finals, their best performance coming in 2004 as hosts when they reached the final, only to lose to surprise winners Greece.
27/02/36 Fr Portugal 1 Germany 3 Lisbon
24/04/38 Fr Germany 1 Portugal 1 Frankfurt
19/12/54 Fr Portugal 0 West Germany 3 Lisbon
27/04/60 Fr West Germany 2 Portugal 1 Ludwigshafen
17/02/82 Fr West Germany 3 Portugal 1 Hannover
23/02/83 Fr Portugal 1 West Germany 0 Lisbon
14/06/84 ECF West Germany 0 Portugal 0 Strasbourg
24/02/85 WCQ Portugal 1 West Germany 2 Lisbon
16/10/85 WCQ West Germany 0 Portugal 1 Stuttgart
29/08/90 Fr Portugal 1 Germany 1 Lisbon
21/02/96 Fr Portugal 1 Germany 2 Porto
14/06/96 WCQ Portugal 0 Germany 0 Lisbon
6/09/97 WCQ Germany 1 Portugal 1 Berlin
20/06/00 ECF Portugal 3 Germany 0 Rotterdam
8/07/06 WCF Germany 3 Portugal 1 Stuttgart
19/06/08 ECF Germany 3 Portugal 2 Basel
Head to head
Germany 8 wins
Portugal 3 wins
Key: WCQ = World Cup qualifier, WCF = World Cup finals, ECF = European Championship finals, Fr = Friendly
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