The former Carlisle and Blackpool boss will assist new head coach Matt Taylor as they join the club this week.
McDonald has extensive coaching experience across all levels of the English game and Walker insists his appointment is key to success at the Banks's Stadium.
He said: "I think it's a master-stroke bringing in Neil. It's perfect.
"He's been around football. I know him and he's a cracking fella.
"He's a proper football man and knows the game. He's got the experience of when to make tactical changes within the game, which is the most important thing for me.
"Coaching the identity and philosophy is one thing, but you still need results. You need to make the changes at the right time.
"Having Neil behind him (Taylor), who has been there and seen it, it could work really well. I'm really excited by it.
"It fits with what the club was trying to achieve. It's a fantastic thing for the club to do."
After a difficult 2020/21 campaign, Walker insists Walsall's focus this season should be to get supporters back on side with entertaining football – while aiming for a push towards the top of the table.
"The most important thing this season is getting everyone back on board – get the fans back on board," he added.
"Build up a squad that can compete. The fans don't want to hear about a mid-table finish, that's pretty boring.
"If they see an exciting brand of football that gets them on their feet, singing their songs again, that's a massive thing for the club this year. Get them to buy into it."