Derrick Kosinski may be competing on his own during The Challenge XXX, but the three-time champ just paid tribute to one of his most memorable teammates.

"Ran into some old school pics the other day #FBF," the Road Rules alum captioned the photograph above with his Fresh Meat partner Diem Brown. "When the spirit lives, the soul never dies. #AngelsOnEarth We miss you D and know you're still watching."

A brief D-squared rewind: The duo forged a special friendship when they were paired up on the 2006 installment. Diem memorably confided in Derrick that she was suffering from ovarian cancer and opened up about her upcoming treatments -- which were scheduled to begin when this once-in-a-lifetime experience ended. Despite Diem's uphill battle to recover, the two performed well throughout the Australia-based program -- and ultimately finished in fourth place (narrowly missing the finals). From there, Diem revealed her positive prognosis at the Fresh Meat reunion -- and during subsequent years, they both competed on The Duel and The Ruins. Diem sadly lost her battle with cancer in 2014 at the age of 34.

Share your favorite Derrick/Diem memories in the comments -- and don't miss a brand-new episode of The Challenge XXX featuring Derrick on Tuesday at 9/8c.