MANCHESTER, N.H. -- Sem Robberse saved the best for last Saturday, and he may have given more than Toronto something to think about along the way.

The Blue Jays' No. 7 prospect set a career high with nine strikeouts and allowed just one unearned run on three hits and one walk over six innings in Double-A New Hampshire’s 5-1 win over Harrisburg at Delta Dental Stadium in the MLB Pipeline Game of the Month.

The lone tally against the 20-year-old right-hander came in the first inning when top Nationals prospect Robert Hassell III reached on an error by second baseman Hugo Cardona and then scored on a double by the following hitter, Wilson García. A single by Trey Harris and walk by Jackson Cluff loaded the bases before Robberse escaped with a punchout of Yasel Antuna.

“I can't really do much about it,” Robberse said of the first inning. “I was already making good pitches. So I was just sticking to it, maybe adding a little bit more conviction into it, and it worked out the rest of the way. I made sure I didn't really get into my own head and just kept doing the same thing. It worked out.”

After Darren Baker’s two-out single in the second inning, the Netherlands native didn’t allow a single Harrisburg baserunner the rest of the way, retiring the final 13 Senators he faced. Robberse left after the sixth frame having thrown 83 pitches, 55 for strikes with 14 whiffs.

Of those 83 pitches, Robberse felt like the offspeed ones were the keys to his Saturday dominance. He experimented with a different feel to his changeup in his previous bullpen work and found a grip that he could locate much better -- an important detail against a Harrisburg lineup featuring six left-handed hitters, highlighted by MLB's No. 23 overall prospect Hassell, who struck out in the second and grounded out against Robberse again in the fifth.

“I just made sure I was able to stay loose with it, not do too much with it and trust it,” he said. “Tonight, it came up big time.”

The 6-foot-1 hurler was also able to keep the Senators out of whack by constantly flipping in early low-80s curveballs that dropped in the strike zone and gave him an early advantage.

It was his first six-inning performance since July 13 with High-A Vancouver and easily the best of his five outings since debuting with New Hampshire on Aug. 20. He completes his first go-round with the Fisher Cats with a 3.65 ERA, 19 strikeouts and 10 walks in 24 2/3 innings.

“It’s not like in High-A the stuff is worse,” Robberse said. “It's just the consistency of it is better here in Double-A. That's what I had to find a little bit, the consistency and the conviction in all my pitches. I feel like when I'm able to do that, I have control of the game, and I can do pretty much what I want.”

Robberse, who sat in the low-90s with his heater for much of Saturday, adds that his plan is to work on adding strength in the offseason in the hopes of supplementing a few extra ticks of velo to his fastball.

There could be some international decision makers interested in that development.

Robberse says he’s been in touch with Netherlands officials about a potential roster spot on the nation’s World Baseball Classic pitching staff, but those initial conversations have been as far as he’s gone to this point. That doesn’t mean he treated Saturday’s final start as an audition either.

“If they think I'm good enough, then I'm good enough to join them,” Robberse said. “If they think otherwise, then it's up to them. All I can do is put up numbers, and I believe I did that. It's still no guarantee.”

Sometimes, a good start is just a good start. And this is one Robberse plans to carry with him for a few months.

“It’s an upwards trend,” he said. “So I like to see that, especially going into the offseason. I’ll have that boost of confidence in being able to compete next year, at this level too probably.”