Jen-Ho Tseng's game is built around control, and at his best, the right-hander is as close to perfect as anybody in the Minors. The Cubs' No. 8 prospect was at his best Thursday night, and indeed, perfection nearly followed.

The Taiwanese right-hander took a perfect game into the seventh inning and worked a career-high eight frames for Class A Advanced Myrtle Beach on Thursday, but ended up with a hard-luck loss in a 1-0 Winston-Salem win.

The 20-year-old filled up the strike zone, throwing 64 of his 86 pitches for strikes. The eight-inning stint smashed his previous season high of six, and he worked without a walk or hitting a batter for just the third time in 14 starts this season. His outing included a nine-pitch sixth, with all nine going for strikes or balls in play. He finished the gem with two hits allowed and five strikeouts.

The perfect-game bid ended with nobody out in the seventh. Outfielder Adam Engel did the damage, singling on a ground ball to left field. It was Engel's second time playing spoiler against the Pelicans this year -- he ended Duane Underwood's perfect-game bid on April 18 with no outs in the final frame of a seven-inning game.

Tseng was a breakout performer in 2014, posting a 2.40 ERA in 19 appearances (17 starts) with Class A Kane County in his first stateside season. His control was his best asset -- his 1.3 walks per nine innings were the fewest among all Midwest League pitchers with at least 100 innings.

The right-hander hasn't replicated that same exceptional control this year, walking 2.6 per nine. The uptick was in part a calculated decision. Heading into 2015, Tseng opted to sacrifice some command in exchange for some extra velocity, telling MiLB.com in May he'd added 2-3 mph to his low-90s fastball by rearing back and focusing less on location.

Tseng said he's ditched that plan over his past few starts, and his results have improved. He tossed five scoreless innings against Salem his last time out, and Thursday's gem lowered his ERA to 3.91 -- after sporting a 4.66 mark following his June 27 outing.

"I was concentrating on throwing harder, and now I feel that I throw hard enough," Tseng said. "So in the games recently, I'm just focusing on having my best command and locating the ball inside and outside."

The inside heater was a particularly sharp pitch for Tseng on Thursday, and allowed the right-hander to unlock his changeup and also then attack the outer half. The command also helped him induce a season-high 10 groundouts.

"The fastball is one reason and another is I had a better changeup," Tseng said. "Those changeups mixed with those fastballs (helped) make them hit more ground balls and make more groundouts."

After his hit, Engel advanced to second on a bunt by second baseman Jake Peter, then came around to score on a single to right by third baseman Trey Michalczewski. The outfielder narrowly evaded the tag attempt from Myrtle Beach catcher Jordan Hankins on the play at the plate.

Tseng recovered and faced the minimum after that, helping himself with a flashy catch to end a double play in the eighth.

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Winston-Salem's Matt Heidenreich countered Tseng's gem with seven shutout innings, limiting the Pelicans to four hits and a walk while striking out five. The 24-year-old right-hander has a 2.62 ERA in 15 starts with the Dash this year.