Forster has made a phenomenal return from a long-term knee injury, helping Saints go six matches unbeaten, without conceding a goal.
If he can keep Chelsea out for the opening 35 minutes of today’s game at St Mary’s then he will pass Paul Jones’s club record of 666 minutes without being beaten.
Speaking to Southampton’s official YouTube channel
, Fonte said: “Obviously, the return of Fraser Forster was massive for us. Having said that, Maarten [Stekelenburg] did fantastic for us as well – great credit to him, they push each other very hard daily.
“Fraser came back and instantly he made an impact with his presence, with his great ability. He's probably the best goalkeeper in the country at the moment, without a doubt.
"He was out for nine months. To come back and perform like that is not easy, and it's great credit to him and to the staff that brought him back at this level.
“It's unbelievable how a player can come back, and come back maybe better than he was before, so that shows that he worked very hard, alongside his staff, and that shows as well the belief that we have in him, because as soon as he was back we looked perhaps more comfortable and more relaxed.
“Like I said before, he's probably the best in the country and in Europe at the moment, no doubt about it, so I hope that he can keep another clean sheet on Saturday.”
If Forster can keep a seventh successive clean sheet, it will mean Saints tying the club’s top-flight and post-war record, set by Jones and his teammates back in 2001.
Since his return, Forster has been keen to divert the praise onto his teammates, and, while Fonte agrees the defensive form is down to the side as a whole, the centre-half has also highlighted the England international’s part in it.
"We know how important he is,” he said. “You saw the Arsenal game, and the game that he had there. You saw the save against West Ham, which was a very important save.
“He's a humble guy, he knows that by himself he will not be able to keep clean sheets, but he's a big part of it, and he should be proud of what he's doing.”