The 24-year-old attacker has already struck four times in Brazil, sitting alongside Brazil's Neymar and Argentina's Lionel Messi atop the Golden Boot standings.
Low revealed how impressed he has been with Muller, who claimed the top-scorer prize in the 2010 World Cup in South Africa, and believes the Algerian back four will struggle to contain him in their last-16 clash.
"Back in the pre-tournament phase it was clear he was in unbelievably good physical and mental shape," the 54-year-old German told a press conference.
"All our opponents find him hard to handle because his runs are very clever and he keeps popping up in the box.
"He's been in great form for weeks now, and with him I have the feeling the moves and runs come easily to him."
Germany and Algeria face each other in the second round in Porto Alegre on Monday.