The St. Louis Cardinals are in no-man’s land.

The franchise built a dynasty in the National League Central Division by not mortgaging the future for the present, and it has worked.

General Manager John Mozeliak has, for the most part, stayed away from splashy off-season free-agent signings and knee-jerk trade-deadline deals, instead relying on young, talented and cheap players to supplement stars like Matt Holliday, Matt Carpenter and Yadier Molina.

And it has worked.

But all of a sudden, the Cardinals look too old and too young.

They got swept by the Pittsburgh Pirates to open the season and lost two of three to the Chicago Cubs last week.

They have had success against bottom-feeders like the Atlanta Braves, Milwaukee Brewers and San Diego Padres, piling up a 7-2 combined against the three teams this month.

But the underlying problem remains: there might not be a player on the roster in his prime.

Holliday is 36 years old, hitting .228 and on pace for the third-lowest slugging percentage (.474) of his career.

Carpenter turned 30 in the offseason and has struggled at the plate this season, posting a .227 average.

Molina is hitting .338, but is coming of a second thumb surgery that leaves the 33-year-old one foul ball away from a lengthy stint on the disabled list.

That has pushed more offensive responsibility on younger players like Stephen Piscotty and Randal Grichuk, who are expected to be the core of the Cardinals lineup for the next half-decade, but appear to be at least a year away from being The Guy on a contending team.

If not for 28-year-old rookie Jeremy Hazelbaker and career journeyman Jedd Gyorko, who have combined to hit eight home runs and drive in 18, the offense would be flailing.

That’s not a good sign, because the defense wishes it was flailing.

Rookie shortsop Aledmys Diaz can hit (.480 average) but plays defense like he’s on skates.

Second baseman Kolten Wong can’t hit (.208) and plays defense like he’s on skates.

The middle-infield duo has combined for eight errors thus far, and the rest of the defense hasn’t been better.

St. Louis ranks last in the Major Leagues with a .972 fielding percentage and 19 errors.

So maybe Jason Heyward was right.

The former Cardinal right-fielder signed with the Cubs this offseason, explaining in his introductory press conference that he didn’t want to sign a long-term deal and restart with a new core of players shortly after.

The Cardinals’ core, which includes Holliday, Carpenter, Molina and Adam Wainwright, is over the age of 30 and has — at most — one more year together.

Holliday’s contract is up after next season, and it’s hard to imagine the Cardinals resigning a 38-year-old power hitter.

The Cardinals have a club option on Molina’s contract for 2018, so both players could be gone in 18 months.

Wainwright, with his 7.25 ERA, will be 37 when his contract is up in 2018.

Heyward appears prophetic in his questioning of the Cardinals’ future roster makeup.

But he probably didn’t think his prediciton would ring true so soon.

The Cardinals have dominated their division for the last decade by mixing talented youth with proven stars.

But as the older core ages and the younger group goes through growing pains, the Cardinals might be stuck watching Heyward celebrate on the north side of Chicago for a few years.