A brace from Andy Cook saw the Saddlers triumph over the four-time European Cup winners at the Banks’s Stadium last night.
In what was Walsall’s best performance of pre-season so far, Keates sprung a surprise by naming five trialists in his match day squad – four of whom were defenders.
Tom Brewitt, who also played against Villa, is understood to be one.
While eagle-eyed fans in the stadium suggested Christian Mbulu, formerly of Millwall, and Tomas Egert, formerly of Burton, maybe two of the other three.
“They acquitted themselves well - to turn up at 6pm and find out you’re straight in the team isn’t easy,” Keates said.
“We also had to manage them in terms of their fitness. A few have had minutes for other clubs they have been on trial at this week, one got 90 minutes.
“But fair play to the lad, he has come here 48 hours later and pushed himself again. He is trying to earn a contract."
Keates admitted Walsall need to press on with signings with Jon Guthrie the only senior centre-back available.
But he said he won’t be rushed into a decision on his trialists.
“We know have got to get deals done quickly,” Keates said.
“We have got offers that we’re waiting on but I’m starting to get the feeling one or two might not happen.
“The trialists did well but we won’t be making any knee-jerk decisions. We will look back at the video, have a closer look and then maybe we’ll hold talks with their agents.”
Overall though, the boss was pleased with his team’s display against Ajax.
“We were disappointed to lose two previously but I wouldn’t allow us to get too low after losing to Villa and Stoke and now we won’t get too high,” he added.
“But credit to the lads, our performances have progressively got better.
“We played well against Ajax and in the first 15 minutes we could have had a couple. But we kept going.
“We got put under a lot of pressure at times. But against Villa and Stoke we got pulled apart at times, there were too many gaps.
”We have looked at clips from the Stoke game and learnt lessons, the players are taking the information on board.”