FOXBOROUGH – It’s quite possible we’ll finally get to answer the question that’s been nagging at the heart of every Patriots fan: What happens when Tom Brady finally gets hurt?That dreaded nightmare is a lot closer to becoming a reality today with reports (unconfirmed, still, by the team) that the National Football League’s reigning MVP tore his anterior cruciate ligament after being hit on the knee by Kansas City Chiefs safety Bernard Pollard with 7:38 to go in the first quarter of yesterday’s 17-10 season-opening win.Multiple sources, including NFL.com and radio station WEEI, say Brady is possibly done for the season ? and one source has the Patriots already looking at Chris Simms (son of former New York Giants great Phil Simms) as a possible replacement.For a season opener, this game had everything ? from the very possible season-ending departure of the NFL’s best quarterback (statistically) of 2007, to Brady’s replacement, Matt Cassel, making one of the most spectacular plays you’ll ever see; to a goal-line stand at the end that just about got absorbed in all the rest of the events at Gillette Stadium.Brady had just uncorked a 28-yard bomb to Randy Moss – the type of play that put them both in the NFL history books last season as the most prolific touchdown passer and touchdown receiver – when Pollard, already down on all fours after being knocked down on a blitz by Sammy Davis, rolled into him and hit his knee.The pass wobbled (Moss had to come back to catch it, slipped, and ended up fumbling). Brady went down in a heap. And stayed down.Without knowing any more than this (coach Bill Belichick had no news after the game on his status), the play sent shivers into Gillette Stadium, which went stone-cold silent. It rattled the defense enough to allow the Chiefs to drive the ball all the way to the Patriots’ 43 before they had to punt (pinning the Pats back to their own 2-yard line).It confirmed backup Cassel’s belief that you never know when you’re going to play.”I prepared last week like I always prepare,” he said. “You don’t know when you’re going to get to play, and this was a great example of that.”And it may have, once and for all, solidified Cassel’s claim as the legitimate backup. The Southern California product had a horrendous preseason, but Belichick kept him anyway. And to say Cassel responded with one of the great gut-check moments in Patriots history is actually an understatement.The Chiefs, obviously sensing the Patriots were going to grind it out after Brady’s injury, especially practically touching their own goal line, stuffed the middle ? and stuffed New England on two running plays.Just before Cassel ran the third-and-11 play from the one, Chiefs coach Herm Edwards called time.”We were going to make them punt into the wind,” Edwards said, “so we called a timeout knowing that if they ran the ball, we could call another timeout and try to make them punt into the wind.”Edwards was wrong. Instead, Cassel executed a perfect play-fake to Sammy Morris, found Moss – who had changed his route and outrun his double coverage – and hit him in stride.Moss did the rest of the work, outrunning KC’s Patrick Surtain and Jon McGraw before they finally ran him down at the Chiefs’ 48-yard line (a 51-yard completion).”Randy made a great move to get on top of the guy,” Cassel said. “It was nice to get out of the end zone and get going, get that first pass out of the way, and to have a nice completion like that.”The rest of the Patriots breathed a sigh of relief, too.”It was real good for him to get into the rhythm of the game,” said center Dan Koppen, who spearheaded the line’s protection of Cassel (allowing only one sack). “You have to play with the guys you’ve got, and we believe in him.”Cassel proceeded to take the Patriots downfield, and ended the drive by hitting Moss in the back of the end zone for a 10-yard completion and a 7-0 lead.Cassel certainly impressed Moss.”I know the show must go on,” Moss said. “From a team stand