West Brom lie 16th in the Premier League and had the embarrassment of being beaten by Championship side Reading in the third round of the FA Cup on Saturday.
Di Matteo told the BBC: "I think it's the right opportunity to play Myhill so he can show how good he is."
The Welsh keeper came to the Hawthorns in July 2010 in a £1.5m deal from Hull City, but he has yet to establish himself in the Midlands side.
Press speculation has linked the club with Cagliari goalkeeper Federico Marchetti.
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