Tranmere Rovers have signed former Walsall, Port Vale and Grimsby defender Clayton McDonald on non-contract terms.
The 25-year-old has been on trial with the League Two club, appearing in a number of pre-season friendlies.
"Clayton isn't quite there with his fitness yet," manager Rob Edwards told the club website.
"But I've been encouraged by what I've seen in training and the games, and agreeing non-contract terms with him means he can be included in our squad."
Edwards, whose side begin the new season with a home game against York City on Saturday, added: "He'll get better and better the fitter he gets, and we can sit down and discuss his future with him then."