Jarvis joined Walsall on a loan deal until the end of the season from Norwich on Monday, but has endured an injury-blighted two years at Carrow Road.
The former England international has had to undergo operations on both his knee and ankle since joining the Canaries from West Ham.
But while he hasn’t made a first-team appearance since May 2016, Keates says the 32-year-old is now fit and eager to make up for lost time.
“He (Jarvis) will be in the squad for the weekend,” the boss said.
“He has been training with us this week.
“He has had a bad couple of years injury-wise. But he has fully recovered and he’s looked sharp in training.
“He now wants to play games. He’s had a difficult couple of years. But he is fully fit now and has been training for the last two or three months.”
Jarvis won promotion to the Premier League with Wolves back in 2009.
During his time at Molineux, the winger became a fan favourite with his trickery and crossing ability seeing him crowned the club’s player of the year in 2011.
And Keates believes that delivery is ideal for top scorer Andy Cook.
“He (Jarvis) is a winger who gets balls into the box and I think that’ll suit us,” Keates continued. “It will suit the forward players, especially Cookie who likes to get on the end of crosses.
“He will be a great addition to the squad.”
Liam Kinsella has also been impressed with Jarivs in training – with the midfielder looking forward to playing with the 32-year-old.
“He came in on Monday to train with us and he looks very, very sharp,” Kinsella added. “He will be a good boost to the side and hopefully he can bring something to the team and help us get the results.
“He has a lot of experience and I am looking forward to playing alongside him.”