When the Washington Nationals put right-handed starting pitcher Jake Irvin on the 15-day injured list with a strain in his throwing shoulder, it appeared like left-hander Andrew Alvarez was going to backfill that opening.However, against the San Diego Padres on May 29, manager Blake Butera opted to use an opener in front of Alvarez instead of just starting the 26-year-old. That outing happened to be Alvarez's worst of the season, as he gave up three earned runs across three innings pitched.With Alvarez slated to pitch for the Nationals on June 3, it was notable that Butera decided to just have his lefty start the game. And once again, the rising star delivered as a starting pitcher.Andrew Alvarez Has Career 2.25 ERA as StarterWashington Nationals pitcher Andrew Alvarez | Brad Penner-Imagn ImagesFollowing his performance on Wednesday -- where he allowed just one earned run in 4 2/3 innings -- Alvarez now has an ERA of 2.25 across his six starts and 28 innings pitched in his big league career when used in that role.That is impressive, as the left-hander continues to show why he deserves to stay on the major league roster. Used as both a starter and reliever, his career ERA in the bigs is 2.89 across 11 outings and 43 2/3 innings, which more than proves he belongs at this level.But it's as a starting pitcher where Alvarez has truly been at his best in the majors. Coming out of the bullpen, his ERA is 4.02 across 15 2/3 innings and five appearances. That is a stark contrast to when he starts a game, and it seems clear that Washington should just utilize the left-hander in the rotation going forward. However, for an analytical organization like the Nationals, it's also understandable why they might be hesitant to turn the keys over to Alvarez.What Underlying Statistics Say About Andrew AlvarezWashington Nationals pitcher Andrew Alvarez | Brad Mills-Imagn ImagesPrior to his start on Wednesday, he had a strikeout rate and walk rate of 20.4% and 10.2%, respectively, as a starter. When he's come out of the bullpen, those numbers change to 26.6% and 7.8%. With that low of a K rate and that high of a BB rate as a starting pitcher, it's hard to imagine that he'll continue to have the same amount of success he's had to date, which probably gives the decision makers some pause.However, Alvarez continues to be effective as a starter. When in that role, he's holding opposing hitters to under a .200 batting average. The slug is almost non-existent with the percentage under the .300 mark. He also given up a hard-hit rate that is right around 30% and he's inducing ground balls well over 50% of the time.A larger sample size will be needed before this regime determines if the left-hander can be a long-term starting option for them or not. But right now, it seems clear that he has earned a place in the rotation until proven otherwise.Add us as a preferred source on GoogleFollow