PHOENIX — To steal a phrase from former manager Jim Tracy, it would behoove the Rockies to get an ace-like performance from right-hander German Marquez in the second half of the season. Marquez, naturally, believes his best is yet to come. Manager Bud Black concurs. “With German, there is still growth to be had and his best pitching is still ahead of him,” Black said Saturday night before the Rockies played the Diamondbacks at Chase Field. On Sunday, Marquez, 8-3 with a 4.38 ERA and 120 strikeouts, will make his final start before the all-star break.