The Washington Nationals reportedly have interest in Javier Vazquez, one of the underrated workhorses of his era and a great strikeout hurler. Some people find this mildly confusing, despite glowing scouting reports on Vazquez in Puerto Rican winter ball, because with Stephen Strasburg, Gio Gonzalez, Jordan Zimmermann, Dan Haren and Ross Detwiler on the roster, they have an ostensibly full starting rotation.

Ostensibly so, but not necessarily. For one thing, of course, four of the five players in that rotation have significant injury histories. For another, though, Ross Detwiler is in there.

Detwiler is a left-hander, tall and thin, with a fastball that rarely runs much hotter than 91 miles per hour but who finally (after years of uneven performance and being shuffled up and down) broke out at age 26 in 2012. He dominates lefty batters (.170/.255/.259 last year), but was also better against right-handed batters than the average southpaw. Detwiler is a good pitcher.

Unfortunately, he isn’t especially durable; he doesn’t have elite stuff; and he only gets to face lefties roughly 20 percent of the time as a starter. In the meantime, the Nationals will apparently be using a virtually exclusively right-handed bullpen to open the season.

Detwiler should move. That Nationals should sign Vazquez, understanding that he (or someone else in that rotation) will get hurt during the season, and Detwiler should be recalled to the rotation to address that need as it arises. In the meantime, though, Washington would have every bit as deep a rotation, but would then also have a guy with a 20 percent chance of becoming the next Sean Marshall out in the bullpen to help shred Philadelphia’s and Atlanta’s lefty-heavy lineups late in games.

This all goes to a broader point I have made before, although perhaps not here: Lefties with any sort of non-negative platoon split should nearly always be pitching out of the bullpen. That’s one reason (of many) that I am uncomfortable with the Reds’ choice to move Aroldis Chapman back to the rotation. It makes a modicum of sense in their specific case, because Marshall is a Red and that lefty relief ace is less needed. However, Detwiler should be treated as a reliever until needed elsewhere, and in general, lefties get roughly 250 percent more plate appearances with the platoon advantage if used out of the bullpen. That goes unexploited too often.