The announcement that Martin Truex Jr. will retire after this season took the NASCAR world by storm and left Joe Gibbs Racing scrambling to make its next move. As the dust has settled, the speculation about who will take Truex’s seat has begun. First, though, NASCAR legend Jeff Burton wanted to be sure everyone realizes exactly what the sport is losing when Truex Jr. hangs up the gloves. It’s not insignificant. “You don’t replace Martin Truex Jr.,” Burton said on Motorsports on NBC. “Martin’s one of the most underrated drivers in the sport. If you look at what he’s done since 2016, no one’s wo…