I wrote about the position players yesterday; Adam Jones is clearly playing over his head (we don't know by how much, but I'd wager that he doesn't end the year with 50 home runs), but otherwise things seem relatively reasonable overall. There will be some drop-off there, but maybe not a huge amount.
It's on the pitching side where I think more people are holding their breath. After years and years (and years) of poor pitching, the O's staff has done some work this year. Their 3.44 ERA is probably unsustainable, but the 4.01 FIP and 3.97 xFIP are both better than average as well (if only by a little).
The starting staff has been pretty average across the board overall:
Jason Hammel has been fantastic - 8.5 K/9, 2.9 BB/9, 60% groundball rate. The new two-seamer plus increased use of the slider may really have turned him into a different pitcher. He's not likely to finish with a sub-3 ERA (even if his xFIP is 3.02), but under 4 seems reasonable.
Wei-Yin Chen is matching Hammel in the ERA department (2.66 vs. 2.68), but he's been (a) an extreme flyball pitcher who hasn't yet given up too many home runs, and (b) only solid at striking out batters (6.6 K/9). Thus the almost two run disparity between his ERA and his xFIP (4.43). He certainly looks capable of sustaining that latter figure at least, but the difference between the two in 100 more innings is around 20 extra runs allowed.
Jake Arrieta has had the opposite issue, with an ugly 5.21 ERA but a nice 3.92 FIP and nicer 3.45 xFIP. His strike-outs are up* this year (7.8 K/9), and he's cut his walk rate almost in half (2.2 BB/9).
* Some of this has more to do with getting into better counts by throwing more strikes.
The big problem for him seems to have been some poor luck with men on base:
Unlike the O's offense, a disproportionate number of home runs he's allowed have been with runners on base. That's not likely to continue.
The 3.45 xFIP is probably generous, but he could definitely post to a 4 ERA going forward if he continues pitching like he has so far (what with missing bats and hitting corners). That should mostly cancel out Chen, depending on who can stay healthy and pitch some innings.
Tommy Hunter has given up a ton of homers - 1.8 per nine - while walking more batter (2.6 BB/9) without seeing much of an increase in strike-outs (5.1 K/9). Because he gets more groundballs though, he actually has a better xFIP (4.34) than Chen. Once balls stop leaving the yard at such a high rate, he should be able to settle in as a back of the rotation starter.
Things have been pretty ugly for Brian Matusz this year - 5.50 ERA, 4.62 FIP, 5.03 xFIP - but it's certainly an improvement over 2011. If the fastball command can keep coming back, he might be able to slot in with Hunter in the rotation. Like Chen, Matusz allows a lot of flyballs - but his have found the seats with more regularity (1.2 HR/9). Plus, he's walked way more batters (4.1 BB/9). I've seen enough out of him to think he could improve some, but at least he's not likely to hurt the team worse going forward (if he pitches poorly, he'll be out of the rotation at some point).
Overall, the rotation is probably going to back-slide some. If Hammel or Arrieta miss time, it could get a little ugly. Someone (Zach Britton? Dare I say... Roy Oswalt*?) replacing Matusz - or Brian just pitching better - off-sets that somewhat, but they're probably going to allow (at least) 10-20 more runs than they're currently on pace for.
* Roy Oswalt probably isn't coming to Baltimore even if they have a 10 game lead in July and offer him $15 M.
The O's bullpen has also been doing something we haven't seen in Baltimore in a while - not sucking;
That back end of the pen has been something. Lindstrom being out hurts, but Stu Pomeranz looked impressive in his short call-up and I could see him filling in relatively well later in the season. Dana Eveland out there now is... not the absolute worst.
The full unit's 2.18 ERA isn't going to continue, and how high it rises is going to have a real impact on the team's record. A 3.75 ERA (to match their FIP and 3.71 xFIP) going forward means something like 60 additional runs allowed over their current pace.
Putting it all together, while the pitching staff is set to allow around 652 runs if things keep going as they are, there's a good chance they'll end up allowing between 50 and 75 runs more than that. That's not accounting for defensive regression, of course.
If you say all of the position player decline (maybe ~60 runs vs. current pace) is attributed to runs scored, then that would drop them from 717 to 652 (can't compare to last year since defense is being folded in too).
The team's current run differential, and (obviously) the 717-652 one, both give a ~.543 pythag winning percentage. That's 88 wins over a full season. If the team ends up at 667-700 (minus 50 - plus 50), then that's a .466 winning percentage in the remaining 124 games (75.5 wins over 162 games). As shown yesterday, that would - with their current start - have the O's winning 80-81 games this year. If the team ends up 647-725 (minus 70 - plus 75), that's .417 (68 wins over 162), and they finish with 76 W's. So somewhere in that range - 76 to 81 wins to end the year - seems reasonable enough.
Certainly this is largely guess-work, but the Orioles are very likely to regress at some point (they're not going to win 100 games). Depending on how hard it hits them and how healthy their key players stay, at least the team's first winning* season since 1997 is realistically within reach - and I imagine that 99% of O's fans would have gladly taken that before the season started. The middle of May is still a long time away from October though, so not only would I not print play-off tickets - I'm not even that confident the O's finish above 5th place (tough division, that AL East).