The former Southampton and Doncaster midfielder spent a spell on loan at Bristol City last season and is now a free agent.
"We needed that type of player today (Saturday) so we gave him an opportunity to show us what he can do," Johnson told the Glovers' website.
"If he wants to stick around for a little while longer I'm sure he will get that opportunity to keep impressing.
"We won't make that decision after a day and a bit. I know him very well, he's played against my teams many times and he's still got something in there that can help someone and it could be us."
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