It isn't a claim. Ask the others from the Fifth Holy Grail War and they will support what I say. I, Tohsaka Rin, am the only person capable of winning it at that given time.

[ Frowning, she looks away from the locket, as if what she was going to admit next made her uncomfortable. ]

There was a boy who thought himself to be a hero, but it wasn't something I'd call valor, more like a stubborn itch that he tried to scratch over and over again with no relief. When I told him to run, he wouldn't despite his inability to add any benefit to the situation.

... but at the same time, he was the only one who stood by me when I had no one else to support me.