Forster, who manager Hasenhuttl believes is capable of improving to challenge McCarthy for the number one spot, will initially join Angus Gunn in providing competition, although one of the two back-up keepers may still depart.

"He stays with us at the moment," Hasenhuttl said of Forster. "We have Alex McCarthy as our number one. I think Alex made a fantastic development in the last games.

"Then on the number two position, Fraser and Gunny, one will maybe leave us and the other one will stay with us.

"Especially with the ball, we have created some habits and some automatism that Fraser just has to learn. He definitely can do it because he is also open-minded and tries to improve his game.

"The goalkeeper game is changing all the time, it's developing, especially what you demand with the ball is definitely completely different now.

"Andrew (Sparkes, goalkeeping coach) does it over a year now with Alex and you can see that he's normally a little bit ahead of the other guys."

Saints will be without Stuart Armstrong at Selhurst Park.

The midfielder suffered a quadricep injury on international duty with Scotland, much to Hasenhuttl's frustration.

"Stuart Armstrong came back injured from the national team for the second time, which I really hate because it's a pre-season and I do everything to keep the players healthy," he said.

"And he's coming back after playing 80 minutes, most definitely not perfect, I think.

"That smashes a few automatisms in our game but we have to handle this. But it's not perfect."

It has been a relatively quiet pre-season on the south coast, with defenders Kyle Walker-Peters and Mohammed Salisu the only arrivals.

Hasenhuttl is adamant he will add to his squad before the transfer window closes on October 5.

He is eager to replace former captain Pierre-Emile Hojbjerg, who was sold to top-flight rivals Tottenham, while he remained tight-lipped on a potential move for Club Brugge striker Emmanuel Dennis.

Saints are rumoured to be interested in 22-year-old Nigeria international Dennis as part of a deal for defender Wesley Hoedt, who spent last season on loan in Belgium with Royal Antwerp.

"More needs to be done (in the transfer market), absolutely," said Austrian Hasenhuttl.

"We know we have lost the six with Pierre Hojbjerg and we need on this position an alternative. We will definitely do something in the next weeks. Still time to go.

"We have a good XI but we have a lot of games, so we need to have some alternatives."

Asked about the situation with Dennis and Hoedt, he replied: "I don't want to discuss any rumours.

"We have a few players, they have been on loan and get opportunities to stay on loan or go somewhere else. If that is an opportunity for us, then we take it and bring somebody in – it can be a permanent deal or a loan option. We keep our eyes open."