Listening to the post-game interview with Shelton, Abel was scheduled to come in the 5th inning no matter what happened during the game. I'm in the camp with @Rosterman and had discussed it late in spring training that Abel could have started the year in St. Paul, made one start to get his work in, and then been brought up to the majors to make his next start. This method would have given us another bullpen option, possibly Altavilla, to help out with the bullpen for the first few games.
If you do believe that the piggyback idea could have worked, then you had to be willing to pull Abel when he was getting in trouble after you believe he has enough work in. I could forgive the 6th inning although Abel had coughed up the lead. But you had to take him out in the 7th. He had already thrown 47 pitches in 2 innings. By the top of the 7th, Abel had clearly shown that he did not have it today and should have been pulled. I scoured the pitch-by-pitch summary on mlb.com when Abel had an 0-2 or 1-2 count, The O's hitters went 3-8 with a walk, 2 doubles and a single for an OPS of 1.069 and 4 strikeouts in 3 1/3 IP. I'm even a big Abel fan, but he didn't look like he had it today and was probably misused as a piggyback option and I hope this was just a one-off used because they felt they needed to keep Abel on a schedule.