Heaney, who was acquired from the Dodgers for second baseman Howie Kendrick, was 6-2 with a 4.71 ERA in 14 starts for Triple-A Salt Lake, posting a 1.53 WHIP while walking 2.9 batters and striking out 8.5 per nine innings.
The 24-year-old left-hander posted a 3.02 ERA in his first nine starts, but has given up 27 runs (24 earned) in his past 27 2/3 innings.
Angels director of player development Bobby Scales recently chalked up Heaney's latest struggles to the volatile nature of the hitter-friendly Pacific Coast League, saying he believes Heaney is ready for the Major Leagues.