NEW YORK - Chris Smith, called up as a spot starter right before the All-Star break, might be slowly working his way into Oakland’s rotation. Smith, who put up a 2.77 ERA in his first two starts, will go again for Oakland at Toronto on Monday, with Jharel Cotton heading back to Triple-A Nashville to continue his rehab assignment while returning from blister issues. [...] Smith - at 36, the oldest player in Athletics history to make his first big-league start - is thrilled every time he gets another one. Smith, who has made 63 big-league relief appearances, enjoys the greater room to play the cat-and-mouse game with hitters that a starter is enabled - facing batters more than once means more strategy can be employed with pitch selection and within counts. “Maybe in the third inning, I can think, ‘Hey, I threw this guy fastballs in the first inning, maybe I can go to my changeup here,’ ” Smith said. Coming out of the bullpen, I might have to go to my changeup right away, so I get that little luxury as a starter. Manager Bob Melvin said that because Cotton threw 65 pitches in his last rehab start, the team would like him to continue to build his pitch count up. Cotton has been erratic, with a 5.17 ERA, and another rookie starter, Daniel Gossett, also has had trouble with his consistency, with a 5.79 ERA going into Sunday’s outing at New York.