Twins catcher Jason Castro is expected to be out 4-6 weeks after meniscus surgery slated for Tuesday. News of Castro's surgery made me think a little more about how injuries — and recovery timetables — are presented, and it led me to develop a system of sorts to decode how serious injuries really can be.

Note: The following is not a suggestion that athletes are misdiagnosed or somehow want to miss more time than expected … nor is it assertion that teams attempt subterfuge when presenting initial injury timetables. It's merely a catalog of how things tend to turn out in certain situations — and red flags to keep in mind.

Beware: Injuries to knees and backs. When you're talking about ligaments, joints, tendons and soft tissue, making an accurate prediction for an athlete's return seems to get tricky. A broken bone is a lot easier to pin down than, say, a more finicky injury that can be aggravated easily.

A good example of this includes Zach Parise's back injury this past season. He tried to play through pain but had a setback and continued leg weakness related to his back problems. Parise ended up having back surgery in October and didn't make his debut until early January. Sam Bradford's knee injury in 2017 is another good example. A knee problem that didn't seem serious ended up costing Bradford all but six quarters of his season.

Beware: Recurring injuries. If an athlete is set to miss time with an injury that has already kept he or she out previously, the news might not be good. Parise and Bradford are both good examples again. Wolves big man Justin Patton recently had the second surgery on his left foot in less than a year, and it will be worth monitoring his progress.

Another good example is Castro. He missed the entire 2011 season with a major injury to the same knee that has him sidelined right now, and he's battled off-and-on pain in the knee ever since then. I'm not saying Castro will be out longer than the 4-6 weeks the Twins said upon announcing the injury Monday, but it bears watching.

Beware: A team hoping rest, rehabilitation or some other short-term procedure will fix the problem. Athletes surely play through more minor/nagging injuries than any of us will ever be aware of, and teams are right to hope that surgery can be avoided. But still, disabled list trips and surgeries seem to follow a familiar pattern by which teams initially hope a method will work.

Castro hoped rest would help his knee before surgery became the choice. Same with Ervin Santana, who had discomfort in his finger last year, received an injection in the offseason, then needed surgery in February when the discomfort didn't subside. The original hope was Santana would be back in early May. It's looking more like early June now.

And if a pitcher is shut down with elbow discomfort, with the hope that rest will suffice? Look out ahead for the dreaded Tommy John surgery.

Beware: Hints that recovery is not going well. Miguel Sano hasn't played since April 27 because of a hamstring problem. It went from the hope that Sano would only miss a few games, to a DL trip, to Paul Molitor not sounding very optimistic in recent updates about Sano's return.

"I'm hoping we have a good week here and we can think about getting him into a game sometime, sooner than later, somewhere," Molitor said Monday.

You officially have the right to be nervous about when Sano will actually return to the field.

Beware: Vague long-term timetables. Anytime I hear that an NFL player had offseason surgery but should be ready for the start of training camp, my alarm goes off — particularly if it's a young player and not a veteran who doesn't necessarily need a full camp to be ready in Week 1.

When Patton underwent his second surgery last month, the Wolves said it was to "encourage further healing" of his original injury but said there was no timetable for his return. Maybe that's just to manage expectations, but it raises a red flag for me, particularly after Patton missed summer league and training camp last year as a rookie.

There are of course exceptions to these rules. Jeff Teague and Jimmy Butler, for example, both had knee injuries for the Wolves last season, but both returned to action on a pretty much as-expected timetable.

But keep these things in mind as various athletes progress from injuries — and make mental notes when new issues arise.