Only plug in 8-pin on 8+6 pin card?

Hi,

I ordered 2 Corsair 750w PSUs and 5 Powercolor RX 580s. Each PSU has 5x8-pin connectors. It seems that I will only have an 8-pin connection left after connecting all the cards and the motherboard. Can I just use the 8-pin connector on the card without connecting the 6-pin as well?

Thanks