Cale, the Brumbies' top try-scorer, left the field just 26 minutes into the Super Rugby Pacific clash at Forsyth Barr Stadium in Dunedin on Friday.
Regardless, the visitors overcame the loss of the Wallabies hopeful despite a less-then-convincing performance in which they coughed up 18 turnovers.
"We put him down as a tactical sub. He's part of the nationally medically managed players, so I'm just going to say ... that we took him off for next week," a smiling Larkham told Sky Sports NZ.
"I'm protecting him for the Wallabies' campaign down the track."
The decision to rest Cale came despite the Brumbies having a week off last round, heading into their bye having lost three of their past four matches.
That poor run followed their glittering start to the competition, which had propelled them to the top of the ladder with a 3-0 record.
Friday's win will relieve some pressure on Larkham's team, moving into third spot, one point behind the ladder-leading Hurricanes (25).
Winger Corey Toole was crafty with 63 metres and three defenders beaten, while inspirational captain Ryan Lonergan posted 105 passes and a try in his 100th game.
Allan Alaalatoa, an 88-cap veteran for the Wallabies, returned from a back injury and made six tackles and four passes, while Lachlan Lonergan (three carries, one defender beaten) also played his first match of the season after injuring his knee last July.
The Highlanders made six changes ahead of Friday's clash and struggled to break down the visitors' rigid defence, but a second-half try to winger Jona Nareki did threaten a boilover.
A late yellow card to hooker Henry Bell was costly, despite All-Black Ethan de Groot (16 tackles, nine passes) sparking the home team.
"It was a tough day at the office and a scrappy old game. We had opportunities to win it, and we just fell short," de Groot said.
The Brumbies started slowly, but finally scored the first try when Ryan Lonergan picked up the ball from the ruck and slammed over the line in the 35th minute.
Trailing 7-3 at halftime, the Highlanders piled on the pressure and took the lead when Nareki kicked and caught his chip in the 63rd minute.
Just as the Kiwis looked to ice the result, Bell was handed a yellow card, and the Brumbies capitalised when Luke Reimer crashed over in the 74th minute.
