Here's the forecast for Wednesday, Clay, and I think you can count on this one: Lots of baseball. Due to the April 4th game that was canceled on account of "too perfect game time weather," the A's and Mariners have a double-header on Wednesday.
Both teams can call up a 26th player just for that game, as the A's did with Josh Lindblom to start game 2 of the April 2nd double-header against Cleveland. It's worth noting that Oakland's bullpen is pretty spent going into the Seattle series, with Dan Straily and Tommy Milone going short on Friday and Saturday, and then 4 relievers working in today's 10 inning win.
One option the A's have is the one most being bandied about: Oakland might call up either Lindblom, or Arnold Leon, to start game 2 on Wednesday. Bob Melvin has also not ruled out Drew Pomeranz, who threw 57 pitches on Friday, though his consideration may depend on whether or not he is needed out of the bullpen on Monday or Tuesday.
But wait, there's more...Milone is on turn to pitch Thursday, but the A's have a day off on Thursday, and Sonny Gray is on turn to pitch Friday when the A's open the series against the Washington Nationals. What this means is that Milone could start Wednesday on 3 days rest, which is not unreasonable considering he threw just 77 pitches (74 of which even stayed in the ballpark). In this scenario, the A's could conceivably call up a reliever, such as Fernando Rodriguez, instead of a spot starter.
Or they could play it the way I am going to suggest...
I would like to see the A's select Leon, not Lindblom, to start game 2 of the double-header, based on Leon's upside. You know what you have in Lindblom, and it's "#6 SP filler" and while you might get a winnable 5⅔ IP, 3 ER effort it's from Leon that you are more likely to find another good starter for the rotation beyond Wednesday.
Meanwhile, skip Milone's next start, with Gray going Friday, and put him in the bullpen to be available for long relief in either game Wednesday. This should relieve (literally) a lot of pressure on the weary bullpen to have another luxury long reliever available.
What this also sets up is that should Leon pitch really well and look like a legitimately good option in the rotation, he is on turn to stay in the rotation if the A's want him to take Milone's spot (or Dan Straily's were Straily to really struggle again on Wednesday). It all gives the A's what they most like to have: A lot of options.
So that's my vote, personally: Straily and Leon go Wednesday, Milone to the bullpen for a turn, Gray goes Friday, assess from there. How would you play it, and why?