Colodny and Gettlin both famously claimed that Al Haig was Deep Throat - a less convincing assertion than their case for John Dean as the mastermind of the Watergate breakins.
But I think this does raise excellent questions about Deep Throat. It's possible to think that both Felt and Haig were sources for Woodward - but perhaps not in the ways that are generally now accepted - or represented by Woodward.
Fyi.