Trialist Lee Hills claimed an assist during 90 minutes for Southend's reserves in a 3-1 friendly victory over Braintree on Tuesday night.
The fit-again Crystal Palace left-back, 21, has linked up with the Shrimpers with a view to a possible loan deal having been sidelined for almost two years with knee problems.
Hills sent over an inch-perfect cross from the left for Kane Ferdinand to head home Southend's crucial second goal from six yards.
Midfielder Lee Sawyer, returning to the frame himself after a long-term thigh injury, put United into the lead early on but the non-league hosts levelled matters just before half-time.
The double arrival of substitutes Liam Dickinson and Ryan Hall - who, along with Ferdinand, breached club discipline procedures in the team hotel the night before Saturday's defeat at Morecambe - helped turn the game in Southend's favour.
Ferdinand headed United back in front 10 minutes from time before Dickinson added a third late on from long range.