De Jongh will officially replace injured second row stalwart De Kock Steenkamp (groin), the latter joining Rynhardt Elstadt, Eben Etzebeth, Manuel Carizza, Jean Kleyn and Gerbrandt Grobler as the injured first-choice locks in the DHL Stormers region.
DHL Stormers coach Allister Coetzee said: "De Kock, unfortunately, has suffered a recurrence of his groin injury. He flew home from Australia this morning (local time) and will consult a specialist when he gets home.
"We still have Jurie van Vuuren here who can cover lock and flank and, thankfully, Michael Rhodes is available for selection again this week (after missing the Chiefs match), so we have locks that can start for us.
"Juan is available this weekend, having fully recovered from his knee injury, and has already trained with us (today). He is raring to go."
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In other injury news, fullback Jaco Taute will sit out this week with an injury to his AC Joint (on the other shoulder this time), but tighthead prop Frans Malherbe (broken baby toe) will be available for a starting spot this week.
Big wing Sailosi Tagicakibau is set to make his first start for the DHL Stormers against the Brumbies in Canberra this Saturday, with Gio Aplon likely to start in the No.15 jersey in the absence of Taute.
"Jaco, like we've done with Siya Kolisi, will be continued to be managed (with his AC Joint)," said Coetzee from Sydney on Monday, "but there is good news in that Michael Rhodes and Frans Malherbe are back and available for selection."
Squad captain Jean de Villiers (shoulder) and lock Ruan Botha (knee) suffered minor knocks against the Chiefs last Friday, but both are fine and will be available for selection against the Brumbies on Saturday (kick-off 10h40 SA time).
"We're still very positive about the campaign, but the big thing is that we turn it around against the Brumbies this weekend," said Coetzee.
"I think that we had our big chance against the Crusaders, which we let slip, and we were close to the Chiefs (20-24) with four minutes left.
"My big message to the players earlier today was that this game has ebbs and flows, sometimes it goes against you... other times it doesn't," added Coetzee. "When you have momentum you need to capitalise and hopefully we will learn from this."
The DHL Stormers are in the middle of a tough four-match tour of Australasia, having played against two top New Zealand teams (in the Crusaders and Chiefs) and two quality Australian sides (in the Brumbies and the Reds) lying in wait.
Of their four matches thus far in 2014, three have been played away from home and any points they pick up on the road during the next fortnight will be a huge boost ahead of seven remaining home games at DHL Newlands in April, May and July.
"The Chiefs were a completely different challenge and they asked different questions of us," said the DHL Stormers boss.
"The Brumbies are also a very, very good side. I saw their match against the Waratahs, it was a very physical game and they stood up well (physically).
"Fortunately, I could see our response at training today already, it was much better than last week," added Coetzee. "The two-day rest (having Saturday and Sunday 'off') did us a world of good from a recovery point of view and the guys showed a massive intensity at training today which will help us agains the Brumbies as we need to (once again) put our bodies on the line on Saturday night."