A linner is not a loser in and of themselves, but someone who is or has ended up on the losing side.
A linner is someone who is respected and can hold decent stock, thus it's not a slur but a mark of respect.
(w)inner - Linner
Sterling Moss was a famous F1 driver; he never won a championship, but as the bane of most great drivers we can say he was a linner.