Matthews, 28, has made 137 club appearances across spells at six clubs, including Hamilton Academical.

"We've been searching for a goalie, probably one with a wee bit of experience as well to replace Zander," said manager Davidson.

"I am delighted to get him up and get him ready for Saturday. He is in there to make sure he is ready to go. He has got good experience.

"I thought Elliot (Parish) got stronger as the games went on in the cup competitions and I said to Elliot he has got to make sure he is ready step in if he needs to."

Clark, 30, is a free agent after being on St Johnstone's books for 11 years.

Mitchell, 20, has previously been loaned out to Bromley and Leyton Orient and has 41 club games.

"We watched him last season, he has played a lot of competitive games down the road, a good old-fashioned defender," Davidson said.

"Alex likes to defend, he's a Fraser Wright, Steven Anderson type, so we are delighted we got him through the door.

"We have unfortunately had to release Dan (Cleary), he had to go back home for family reasons, so it was important we strengthened that area and made sure we are secure for the start of the season."

St Johnstone open their Scottish Premiership campaign at home to Hibernian on Saturday.