Mueller and Hummels will remain at their northern Italy training camp along with Bayern Munich team mate Jerome Boateng, working back towards full fitness following a muscle injury late in the season.
"Mueller had many games this season, Hummels had many games this season. We know what they can do so it is good for them to clear their head a bit this weekend," Loew told a news conference.
Midfielder Toni Kroos will arrive in Italy on Saturday after a brief break following his Champions League victory with Real Madrid.
Loew said that fellow 2014 World Cup winners Mesut Ozil and Sami Khedira, who suffered late-season injuries, would be on the pitch on Saturday to get much needed match practice.
Surprise addition Nils Petersen will also get playing time against Austria with Loew praising the Freiburg forward, who is battling for a spot in the squad along with fellow forwards Mario Gomez and Timo Werner.
"The impression I have of him has only been getting better," Loew said of the versatile forward. "He is working really hard."
Loew has taken 27 players into his preliminary squad and will cut four of them, including one goalkeeper, on Monday for his final 23.
The Germans are in World Cup Group F with Sweden, South Korea and Mexico. The tournament starts on June 14.
"Not everything is working perfectly yet," Loew said. "But at this stage that is normal. Everything has gone according to plan. We have no injuries after about 10 days and that is a good feeling to have at this point."
(Reporting by Karolos Grohmann; Editing by Christian Radnedge)
