Brendan Galloway says Dutch goalkeeper Robbin Ruiter showed his quality at Glanford Park on Wednesday night.
Galloway sat out Ruiter's debut at Bradford with an injury but took his place in the XI this week to see the 30-year-old impress again.
One outstanding reflex save in the closing stages particularly caught the eye, with Grayson eager to sign the trialist up on a permanent basis.
Sunderland's transfer business continues at a pace and Galloway, the first signing of the summer, says it is a boost for the whole squad.
"I think he’s a really good goalkeeper, you’ve seen from the saves he’s made tonight, especially that one right at the end. I think it shows his quality, the clean sheet speaks for itself. That comes from the defence and the midfield and all the players as well," he said.
"The manager is working as hard as we can to bring in the new faces and it is obviously a positive for all of us."
Galloway was pleased to make his return from injury with the season opener against Derby County just a week away.
The Black Cats laboured to a 0-0 draw but the left-back was pleased with the defensive effort and the extra minutes for him and his team-mates.
He said: "It was good, we’re getting closer to the start of the season and I think we’re all picking up match fitness. I think the team did well defensively, to get that clean sheet, we had a couple of opportunities to go and score. The clean sheet was the main thing.
"I picked up a bit of a knock last week, so to get through 70-odd minutes was good and it is just about pushing for 90 now.
"Everyone is working as hard as they can, as a team and as individuals to impress the manager and hopefully to get that spot for the first game of the season."