Darlington manager Martin Gray is hoping to land a replacement for Gary Brown in time for the new season.
Quakers' captain will miss the kick-off on August 17 after suffering an ankle injury last Saturday at Gateshead, leaving Gray looking to make another addition to his defence ranks.
With Joe Tait having moved to Gateshead, this summer Gray has brought in Chris Hunter while Jordan Robinson arrived at the end of last season.
Sunderland and Middlesbrough are believed to be the clubs Gray has spoken to and he said: "We are looking at bringing in a loan player from a Premier League or Championship club because with Gary being injured we've got a gap at the back.
"I'm still waiting for confirmation so we'll have to wait and see."
Brown's absence is a blow, but Gray is maintaining a stoic approach. "These things happen in football and they are a test for me as a manager and a test for the team and I'm sure they'll rise to the challenge," he said.
Gray has given games to a raft of trialists during pre-season, though most won't be signing and will not play in this evening's friendly at Durham City.
Jamie Poole has joined Guisborough Town, Alex Francis is now with West Auckland and played against Gateshead on Tuesday, while Axel Williamson has played for Bishop Auckland recently.
Striker Tom Atkinson, however, remains with the club having impressed Gray and he will play some part this evening.
Lee Bullock has signed for Whitby Town, but Gray has not given up hope of landing Andy McWilliams, who played as a trialist last Saturday.
The former Stalybridge Celtic left-back has interest from elsewhere, but Gray is hopeful and is continuing negotiations with the Teessider.
Kick off this evening is 7.30pm and admission is £5 adults and £3 concessions.
Among Durham City's summer signings are former Darlington players Stephen Harrison and Josh Gray.