Instead of taking a few days off during Indianapolis' bye week, the 40-year-old quarterback shuttled his children to and from school and went back to work with the Colts' new offensive coordinator, Rob Chudzinski.
He didn't have much choice after last week's surprise announcement that Luck would miss two to six weeks with a lacerated kidney and partially torn abdominal muscle.
''I really thought that he took a big hit in that (Denver) game, but I get the same answer when I ask him how he's doing as you do,'' Hasselbeck said. ''I just know that he's one of the tougher guys you've ever been around. I had no idea it was that bad.''
Luck was believed to have been injured on a high-low hit as he tried to scramble in the fourth quarter against the Broncos.
After briefly hesitating to get up, Luck threw a touchdown pass on the next play and finished the game. Two days later, coach Chuck Pagano broke the news and announced the AFC South leaders would need Hasselbeck to fill in.
Hasselbeck's impressive resume includes one Super Bowl start, three Pro Bowl appearances and two wins earlier this season in place of the injured Luck. But Hasselbeck also knows he'll need help to get the Colts to a fourth straight playoff appearance.
''I told Andrew I'm going to rely on him heavily. We don't win the Jacksonville or the Houston game without his help,'' Hasselbeck said, referring to having Luck on the sideline.
''I pleaded with him, sort of begged him, `Hey, even though you're hurt and you're not with us, I need you to be with us.' He said, `Absolutely.' I just wanted to get him on record just in case anything went down.''
Pagano provided no updates on Luck's health, saying only that he's still considered week to week.
Hasselbeck said Luck attended meetings Monday in a very different-looking quarterback room.
Two weeks ago, Indy changed coordinators and last Thursday, the Colts (4-5) claimed veteran Charlie Whitehurst off waivers.
''We've won with Matt, and we'll win again with Matt,'' Pagano said. ''There are not many guys winning football games with backup quarterbacks right now. But he's a great leader, got great experience, there's nothing he has not seen, still got arm talent, can still make all the throws.''
Hasselbeck was an efficient 48 of 76 with 495 yards, three touchdowns and no interceptions with back-to-back wins earlier this season.
Can the Colts realistically expect Hasselbeck to be that effective for most of the final seven games?
It's a question even Hasselbeck's younger brother, Tim, posed on ESPN last week. On Monday, the Colts' quarterback responded in kind.
''He's a middle child,'' Matt Hasselbeck joked. ''I don't know what to tell you.''
But the bigger issue is no laughing matter - keeping Luck healthy.
The top overall pick in the 2012 draft started his career with 57 consecutive starts, including the playoffs. Now he's about to sit out for the third time in a season that he has dealt with an injured throwing shoulder, a bad ankle, rumors about fractured ribs and now the kidney and abdominal muscle.
Outside team headquarters, most believe the Colts' struggling offensive line is the problem.
The reality is Luck doesn't always do enough to avoid contact when he runs - or shy away from making hits after interceptions. Pagano and others have tried to make it clear they'd rather he limit the risks.
''We're going to talk every day until he figures it out and we figure it out as a team because he knows full well that he can't do that and he can't put himself or this team in jeopardy by doing that,'' Pagano said. ''You love the grit, you love the toughness and all that stuff. Playing the position like a linebacker, you can't. That's his mentality, that's how he is.''
Which is why Indy needs Hasselbeck to keep the season chugging along.
''I know my limitations, so that might be my strength,'' Hasselbeck said. ''But I have a lot of limitations.''
Notes: The Colts activated cornerback D'Joun Smith from the injured reserve-designated for return list Monday, giving them a little more depth in a secondary that has struggled to stay healthy all season. ... Pagano did not have an update on safety Mike Adams, who injured his left ankle against the Broncos.
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