Gatland has overseen a national Welsh record of 11 straight Test defeats, with losses in November to Fiji and Australia after claiming the wooden spoon in last season's Six Nations.
His second stint in charge of Wales has seen the side lose 17 of the 23 tests played and the last victory was over pool opponents Georgia in the 2023 World Cup when they went on to reach the quarter-finals.
"Warren can't all of a sudden become a bad coach with his track record," said Erasmus with his Boks side heavily fancied to thrash Wales in the Principality Stadium on Saturday.
"The players that they have, if you look at them individually, there are some world-class players in there.
"I know the record of losing 11 on the trot is obviously not great (but) whenever we play a team that's backs against the wall... we take ourselves back, just before I took over in 2017, I think we lost 57-0 in New Zealand.
"The next weekend we lost to the same team at Newlands by two points. That was a weekend apart."
Erasmus added: "I just know Warren is a great coach and I know they've got great players.
"It's not clicking quite there. He is a guy who has fixed things before."
Erasmus, who has overseen the Boks win back-to-back Rugby World Cup titles, said he last caught up with Gatland at Twickenham last summer.
"We had a good chat there about the Lions series," he said, with the Boks beating the British and Irish combined side 2-1 in 2021.
"Coaching can become lonely. It's cut-throat.
"Whenever someone is under the pump, you don't wish anything bad on that person. I wouldn't say I'd love him to beat us, but I'd love him to be successful.
"Although we've bumped heads in the past, he's a rugby man through and through. We've had good discussions.
"I've got a lot of respect for him and I hope he gets the rest from everyone he deserves. There won't be a lack of respect from us to the Welsh team.
"We are preparing for the Wales we know."
Erasmus added that the Springboks would be focused on wrapping up their own successful season, with 50 tries scored in 12 Tests in a year that also saw them win the Rugby Championship.
But he conceded that players can sometimes find a performance no one expects under pressure.
"Sometimes you just turn it around because players believe in a coach, sometimes you just say a right word and the players say they are going to do it for the coach and the country," he said.
