Andrew Miller proved to be a boost to the Orioles bullpen

Perhaps the most highly touted prospect traded at the 2014 Trade Deadline was traded for a reliever headed to free agency at the end of the season. The prospect is Eduardo Rodriguez, and he posted an ERA of 0.96 in six starts in AA after the trade. Yet somehow the Orioles, the team that traded the prospect, should not regret this trade at all. Andrew Miller, the reliever acquired from the Boston Red Sox, was electric in a little more than two months with the team, forming a formidable back end of the bullpen with Darren O'Day and Zach Britton.

Miller was among the best relievers in the first four months of the season with the Red Sox, pitching to an ERA of 2.34 and a FIP of 1.69. It seems certain that he would regress to some extent when the trade was made. Yet he was even better after traded to the O's, posting an ERA of 1.35 with a FIP of 1.13 in the final two months of the regular season. In the postseason, he became an even more important part of the team. He was Buck Showalter's most reliable option out of the bullpen, appearing in five games and pitching more than a single inning in four of those outings. He was entrusted to face lefties and righties, often the heart of the opposing lineup, without allowing in a single run in the playoffs.

Miller has been a strikeout machine ever since he transitioned to the bullpen in 2012. He struck out of 30% of opposing batters in 2012 and 35% in 2013. He was even better in 2014, posting the highest strikeout rate among all pitchers with at least 60 innings pitched at 42.6%. The area where he showed the most improvement, however, is cutting down his walks. Miller has always been wild, never posting a walk rate below 10% even after his transition to the bullpen. In 2014, he finally learned the value of avoiding free passes, cutting his walks by almost half to 7%. The career-best peripherals inevitably led to his career-best numbers. Although he did benefit from a low BABIP of .263, his peripherals suggest that he is indeed among the best relievers in the game.

Miller would definitely be highly sought after in the free agency market, being one of the best relievers despite having no closer experience. By Steamer projections, he is projected to post the 10^th lowest ERA at 2.41 among all pitchers. The O's would definitely love to bring Miller back. However, the O's are caught in a tight spot with their payroll that this seems rather unlikely.

Using the projected arbitration salaries by MLBTradeRumors, the O's are estimated to pay a total of $56.9 million to players eligible for arbitration. The only players who appear to be in danger of being non-tendered are Tommy Hunter and Brian Matusz. Even if the O's let go of both relievers, that would only clear a projected $7.1 million off their books. Adding that number to the $52 million already committed to players under contract, the O's would already have around $102 million in payroll without factoring re-signing Nick Markakis and/or Nelson Cruz and adding other free agents. The O's had a payroll of $107.5 million in 2014. Even accounting for some growth of payroll, it's nearly impossible for the O's to re-sign all three of Markakis, Cruz and Miller.

While Markakis and Cruz raise some questions about an overcrowded outfield (Adam Jones, Steve Pearce, Alejandro De Aza, David Lough), the O's appear to have their priorities set on Markakis and Cruz. Miller may only be an Oriole for less than half a season, but he would be a memorable one given his key role on the 2014 AL East Champion in the playoffs.