The Mariners are presenting a positive outlook on the health of one of their most valuable arms, even with Matt Brash landing on the 15-day injured list Friday with right lat inflammation. The club plans to be cautious with Brash’s recovery ; he will be shut down from throwing for up to five days, general manager Justin Hollander said.  Overall, Hollander said, the club is encouraged at the results of an MRI, which showed no structural damage in Brash’s lat muscle. “The one definitive thing we can tell based on what we saw (from the imaging) is that it’s not bad-bad,” Hollander said Friday afternoon. “No signs of anything serious structurally. Some trace inflammation. … But very good news all around. Probably the best news we could have possibly hoped for.” Brash exited Wednesday’s game in Minnesota after just two pitches in the eighth inning after feeling discomfort in his side.…