Why is the bullpen so difficult to upgrade at the trade deadline?

In response to some of the recent articles that focus on trade options for the Orioles at the trade deadline, some have commented that adding a reliever to the bullpen is just as important as upgrading a position player such as 2B or C. There is perhaps some truth to that, as the O's bullpen has not been particularly deep, with few (or no, to put it bluntly) reliable options other than Zach Britton, Darren O'Day and Ryan Webb. However, we all know that relievers are volatile at this point and their impact is limited by the number of innings they pitch. Even though the innings the key relievers pitch have a larger impact on the outcomes of games than starters, the limited number of innings makes it extremely unlikely that a trade for a reliever at the trade deadline can upgrade the bullpen significantly.

There are only so many innings left by the trade deadline. The most innings a reliever has pitched so far this season is 57 by Carlos Torres of the New York Mets, whom I have never heard of. Realistically, the most number of innings a reliever can pitch after the trade deadline is less than 30. ZiPS and Steamer are much more conservative than that, projecting relievers to pitch at most 35 innings for the rest of the season at this point. We can use these projections to estimate the value they can produce in two months given maximum number of innings. By ZiPS, there are only 11 relievers who will accumulate 0.5 WAR or more for the rest of the season. Steamer is even less optimistic, projecting only 5 relievers to top that mark. So a trade for one of the best relievers in the league under the most optimistic scenario (innings wise) would add 0.5 wins to the O's.

Compared with Steve's suggestion of a trade for Ben Zobrist which can add about 1 win to the O's in two months, this does not seem so insignificant. But remember, the relievers the O's can possibly trade for with their second-tier prospects are not the Craig Kimbrels of the league. They are much more likely to be Francisco Rodriguezs, mediocre relievers who pitched to a stellar ERA for three or four months. By the way, what was the point of trading for Rodriguez to be your mop-up man, which was essentially his role after the trade?

It's easy to say that even if the replacements for Evan Meek and Brian Matusz perform at replacement level, the O's would be better off for the rest of the season. The problem is that we can never know their performance until they play on the field. Brian Matusz was not expected to produce below replacement level either. On average, they may be replacement level, but in 20 innings, anything can happen. This is the same reason why Evan Meek used his magic during spring training to convince Buck to pitch him in crucial situations. Relievers pitch so few innings that the difference between one mediocre reliever and one above-average reliever is minimal, especially in only two months. Hopefully the O's would learn their lesson from last season's trade of Rodriguez not to pay for relievers at the trade deadline again.