Tonight the Mariners open the second half of their season with the most important series to date, hosting the division rival Astros, who are positioned to take over first in the AL West with a strong showing at T-Mobile Park. The Mariners slid into the break with a disappointing last month ending with a disastrous series against the Angels; meanwhile, the Astros have reloaded their pitching and have been playing the best baseball in the league over the past month. They come into T-Mobile Park with all the momentum, and it’s not overselling it to say this is the playoffs, round one, if the Mariners aim to keep any hope alive of their own run at the playoffs and not let the Astros run away with the division.