Watson, Mahan, Henry and Jacobson have already committed to returning this year.
"These past champions, the fans take them very personal here," Grube said. "They remember and these are their champions. This is our champion. So, when you have your champion go on and do something as special Bubba did, people took that personal here. People were very excited and he's excited about coming here. This is a special place for him."
Many top golfers traditionally take a break the week after a major, which also makes building relationships important for Grube.
He also has early commitments this year from other top names such as Anthony Kim, Vijay Singh, Padraig Harrington and Webb Simpson.
But Grube said he knows many people will come to the tournament hoping to find tomorrow's stars, such as Cantlay, who set an amateur record by shooting a 60 during the first round of last year's Travelers.
"Patrick Rodgers, he's a freshman at Stanford, and the No. 2 amateur in the world, and he's got a great track record," Grube said. "He's a guy who could come out and do it. Ishikawa's the only player to shoot a 58 in a professional event, and he could do it.
"There's lots of great storylines with our exemptions that we are excited about."