Manchester United former player Saha was interviewed recently. He said that Manchester United needs goalkeepers like Martin, and some of Onana's mistakes do not meet the standards of the Red Devils.
Saha said: "Martinez is a winner and a leader, and he has such temperament. And Martinez will definitely bring the balance that Onana failed to show last season. Yes, Onana is a confident goalkeeper, but he made too many mistakes.
"Of course, this does not mean that Martinez will not make mistakes, because the risk of goalkeepers in this position is very high. But what happened to Onana last season was something I've never seen in Manchester United or any giant goalkeeper, and that's really unbelievable. I think Onana knows what people are talking about, too.
"I think the competition for position will be beneficial. Onana needs to realize that he has to do better. That performance is unacceptable. We are all humans, but some mistakes do not meet his standards and do not meet Manchester United's standards. Martinez has won the World Cup, and he has made great contributions to both Argentina and Villa over the past three years. He is definitely a good enough goalkeeper."