The first inning was all you needed to see. The Mets’ (18-20) journey to rock bottom reached another level during their 5-0 loss in the rubber match of a three-game set against Cincinnati Reds on Thursday afternoon. Kodai Senga dug the Amazins into a hole from the get-go. The 30-year-old surrendered four runs in the top of the first as the Reds strung together a series of hits and walks capped off by Kevin Newman’s two-RBI single. The right-hander managed to provide Buck Showalter some length going five innings but surrendered a solo shot to Spencer Steer as a parting gift in the bottom of the fifth.