Rojo suffered “significant” knee ligament damage during Manchester United’s 2-1 win over Anderlecht last week and will miss the rest of the season.
He had, up to that point, been an imposing asset at the back for Jose Mourinho, making a total of 41 appearances in all competitions ever since being introduced to the starting XI back in November.
And Herrera, when asked about his teammate, was full of praise for the way in which Rojo had remodelled himself under the Portuguese this season.
“For Marcos, only because he was in the best moment of his career. He was very focused on what he was doing,” he said.
“For me, at the moment he was one of the best centre-backs in the world. Very difficult to beat him, every duel he won, every tackle he won.
“He has to know that he can be back as good as he was. He is my friend and I will try to be very, very close to him to support him and help him.”
It felt as if Rojo was mounting a resurgence similar to that of Chris Smalling last season: instant, hugely effective, blooming with confidence and virtually untroubled as he continued to cement himself further in Mourinho’s starting XI, slowly becoming the focal point of his defence.
Until now, of course. Any victim of a long term knee injury will tell you that, regardless of your form prior to being sidelined, you go back to the drawing board. The process of teaching yourself back to compete functionality feels like it never ends.
But Rojo will have to take confidence from the fact that he had, over the last few months, produced a standard of defensive prowess that nobody thought he could reach. He will have to do the same upon his return – whenever that may be.