John Mozeliak's greatest weakness this year: The Cardinals' 40-man roster

The 40-man roster in Major League Baseball is an area where general managers can make marginal moves to improve the output of the team. Only 26 players can be on the major league roster at a time, but anyone on the 40-man can be called upon to provide at the highest level of baseball.

This portion of team construction has been John Mozeliak's greatest weakness recently. He has done well at making trades these last two years, as he acquired several players last year at the trade deadline who have built up a weak farm system, and Mozeliak made some deft trade moves this deadline to improve the St. Louis Cardinals for the home stretch.

Drafting and development, something that doesn't fall directly under Mozeliak's purview, has also been better these past few years. Players like Tink Hence, Quinn Mathews, Cooper Hjerpe, and Masyn Winn are performing similarly to their projections as top players in the organization.

Rather, the issue that has plagued John Mozeliak most this year -- and in turn made a direct impact on manager Oliver Marmol and the team -- has been roster construction, specifically the 40-man roster. There are several aspects to the 40-man roster that are important to dance around: the injured list, designations for assignment, and promotions/demotions of players.

There have been several instances this year where the use of the 40-man roster has been lackluster by the team's president of baseball operations. For about a four-week period in May, the Cardinals were desperate for a fifth starting pitcher. Steven Matz had gone down with a back injury on May 1st, and the Cardinals were now short one starting pitcher. For quite some time, the team was hesitant to name a fifth starter.

Rather than promoting a pitcher from Triple-A Memphis like Gordon Graceffo, Sem Robberse, or Michael McGreevy, John Mozeliak rolled with just four true starters in May. Matthew Liberatore, someone who was thriving in the bullpen to start the year and wasn't built up to be a starter, was given spot starts, but it took quite some time for the organization to commit to Andre Pallante for that role. This indecision hurt the bullpen corps, and it likely stalled Liberatore's production this year.

Another indictment on the front office this year regarding the 40-man roster has been in regard to the team's insistence on maintaining veterans Matt Carpenter and Brandon Crawford. Both players are lefties, both have limited use defensively, and both have been essentially non-factors offensively this year.

Crawford's role on the team is leadership-based and to give rookie Masyn Winn a break once every 10 days. Carpenter is the 26th man on the roster, so his playing time was supposed to be limited anyway. He's provided leadership that has been necessary, but from a playing perspective, Carp has not contributed much either.

These spots could be filled by rising young players like Jose Fermin, Thomas Saggese, and Luken Baker. Those three provide higher ceilings, they're cheaper, and they provide much greater versatility on the field.

The most recent instance of misuse of the 40-man roster came when Michael Siani went down with an oblique injury in early August. Siani had become a fixture in the outfield for the Cardinals this year due to his defense, and he had begun showing signs of life offensively. Similar to the beginning of the season, the organization rushed Victor Scott II to the majors. He had just started showing signs of success at Memphis, but rather than allowing Scott to build up his confidence offensively, the organization decided to push him to an uncomfortable spot in the majors.

The Cardinals could have added outfielder Matt Koperniak, a player who is slashing .313/.368/.506 with great defense in the outfield. This would have required a move on the 40-man, as Koperniak isn't there currently. The Cardinals have ample players who could be removed to make the necessary space for the young outfielder. Instead, Victor Scott's progress in the minors is interrupted once again.

Great teams are able to thread the needle in more than one way, and John Mozeliak hasn't been able to do that with the 40-man roster this year. There have been opportunities for the team's POBO to make moves that will improve the team greatly, but he hasn't taken those opportunities.