The race to provide a key bit of infrastructure for bitcoin (BTC) ETFs – custody services – hasn't actually been much of a race so far. Crypto exchange Coinbase (COIN) has dominated so far, winning the job from nearly every firm that wants to list an ETF, including BlackRock, Franklin Templeton and WisdomTree.

That's left a giant player in the space, BitGo, on the sidelines – an eye-catching omission.

Only one company that wants to create a bitoin ETF in the U.S., Hashdex, has yet to pick a custody partner. BitGo CEO Mike Belshe confirmed in an interview with CoinDesk that his company is working with "many" of the applicants, opening the possibility – albeit a slim one now – BitGo might show up yet.

"I think Coinbase is the obvious solution on the custodian side and it makes sense that they're the most common," Bloomberg Intelligence ETF analyst James Seyffart said. "But there are some others," he added.

Seyffart said he wouldn't be surprised to see BitGo appear on someone's bitcoin ETF application eventually. Crypto exchange Gemini recently became the first third-party custody partner on an application, appearing in VanEck's.

Custody is an important part of the effort to bring a spot bitcoin ETF to the U.S. market. Custodians hold onto assets on behalf of someone else. In this case, that means safekeeping the (presumably billions of dollars worth of) bitcoin that ETFs will own, keeping hackers and any other bad actors at bay.

Coinbase, run by CEO Brian Armstrong, currently is the custodian for nine of the 12 proposed bitcoin ETFs in the U.S., a level of concentration that makes some uneasy. With Fidelity deciding to custody their own assets and VanEck picking Gemini, that leaves only one application that lists no custodian.

"Having so much bitcoin concentrated in one custodian is not exactly ideal, and I think it would be beneficial for other quality exchanges to participate as custodians for ETFs," said Brian D. Evans, founder and CEO of BDE Ventures.

But it's tough to find other contenders, given the lack of regulatory clarity in the U.S., so the list of suitable companies is short, he said.

"While I do think it's notable to have a majority of the products choosing Coinbase, and I understand why people might be concerned, I don't think it's a problem as long as the security at Coinbase is sound," Seyffart said. "We probably need to see how things play out over the coming months and years."

CORRECTION (Nov. 27, 2023, 21:11 UTC): The story initially didn't note that VanEck had picked Gemini as a custody partner and neglected to mention several other applications in which Coinbase was named as custodian.