My friend Dick is a diamond. He is a champion on the dance floor, and the other night, we were dancing, and exhausted, I fell asleep on his shoulder but we were actually moving quite fast. Anyway, he ripped his shirt, so I darned it in silver thread. 
To darn a rip like this, cut away loose threads, and build up rows of running stitch across the rip, keeping it loose and flat. The ideas is to replace the weave that has been disrupted, not 'stitch it together'. When the running stitches are in place, weave in and out of them along the length of the rip, until it feels strong. Press flat.