The Saddlers saw their winless run stretched to seven matches when they were beaten 2-1 by Scunthorpe on Saturday.
Prior to that defeat, it was announced Russell Martin had terminated his contract at the Banks's Stadium by mutual consent.
Keates snapped up the 33-year-old back in October to add some much-needed experience to his squad.
And Keates, if he can afford to, would like to replace Martin with another senior professional.
"I chipped away at Russ for a long time, he came in with a wealth of experience," the boss said.
"He played at a lot higher level. It maybe took him a little bit of time to be back in League One football.
"If we can add experience, we will – but with experience comes quite a big price tag.
"I made phone calls all last week and we were a bit unfortunate not to add the ones that we wanted.
"There’s been a few niggles going around other football clubs so more players will become available this week.
"We also missed out on a centre-half. He chose to go somewhere else in the division.”
Keates also revealed on Saturday that Jack Fitzwater will not rejoining the Saddlers on loan as expected.
And with just two centre-backs at the club, he knows he needs reinforcements as soon as possible.
"They (Albion) decided not to send him (Fitzwater) back," Keates continued.
"We will look to add a few more bodies this week. We won’t be hanging about."
With Walsall currently in a poor run of form, Keates believes new signings are needed to give both the players and Saddlers' fans a lift.
“I think everyone needs a lift," he added.
"Fair play to the fans, they stayed with the players as long as they could against Scunthorpe.
"There were a couple of moans and groans at the end but I’d say that’s more to do with the result.
"The players gave everything, we can’t question that but we need to find a win from somewhere and get some points on the board."