Going into this year, Britton had pitched primarily as a starter but was barely above replacement level. He was moved to the bullpen this year and he has rewarded the Orioles with a very strong performance. With Tommy Hunter struggling as closer, Britton got a chance to close at least for a night and he rewarded them with a save.
While there's no way his ERA stays below 1 this year (.180 opposing BABIP) I still think Britton has value going forward (assuming he takes over the closer job at some point). His FIP is at 3.41 (compared to 4.80 for last year), and he has reduced the number of walks he's allowed so far. The only area that appears to be stagnant is strikeouts per 9 innings.
My feeling is that Britton has turned the corner enough that if given the closer job in Baltimore he can hold on to it for at least this season and get you some saves.
Like Britton, Lyles has been in the major leagues since 2011 but produced sub-replacement level results over the last few years. In his first season with the Rockies (some would argue his first with a major league ball club), he has gotten off to a fast start.
While his opposing BABIP is relatively low (.255), its not low enough to indicate that his strong start is all smoke and mirrors. So far this year, he has seen his FIP decrease by a run (4.57 to 3.55) so with Lyles I think its a matter of him starting to figure out how to get major league hitters out (he's only 23). I think he'll end up having a solid but unspectacular year in 2014 but there is definitely potential for him to become a very good starting pitcher over the next few years.
His most similar pitcher through age 22 is Javier Vasquez. At age 23, he had an ERA+ of 119, the first of eight seasons where he had above average production and had a nice career as a solid but not spectacular starting pitcher. If this is any indicator, its likely that Lyles is set up to have a productive career.
In both cases, we have players who have been in the majors for three years during which they have struggled and between making solid improvements and varying levels of luck, they find themselves off to solid starts to their seasons. Since Britton's value is tied to whether or not he actually becomes their closer and he's going to get less counting stats (Wins, Strikeouts, etc.) due to not being a starter, Lyles gets the nod here.