The Seattle Mariners will beat the Chicago Cubs at T-Mobile Park on August 21. The victory will be a blow to the 74-54 Cubs who are 2nd in the NL Central and a lift for the 60-68 Mariners who are 3rd in the AL West. Emerson Hancock will be on the bump for Seattle with a 7-7 record, a 3.30 ERA and 1…