Hey SS,
Both the Mariners and Reds are plays that come up in my system, mainly because of the opposition's starting pitcher.
To answer your questions on the Texas/Seattle game...
The Rangers are sending C.J. Wilson, a starter who has yet to go five full innings. He has struggled in his first three starts, all at home, and the Mariners should feel confident they can get to him early.
Pineiro's ERA might indicate that he has struggled too, but he hasn't pitched all that bad in his last five starts. He has gone 6+ innings in his last five starts and has pitched into the 7th inning in all, but one of his home starts (vs. Boston).
Pineiro is also 4-0 at home and 6-3 overall vs. Texas and I think he will continue this success and give the Mariners the lead when he exits the game.
All this being said, I did not want to lay chalk with two teams that are struggling so I decided to parlay them for one unit. I will say that Seattle is the stronger of the two and you should be fine if you decide to take the Mariners straight up.