Niemann threw 50 pitches off a mound on Friday afternoon and called it his best day "by far" in his rehab.
"Felt strong the whole time," Niemann said. "Felt like today was the first day when we had some strength behind it. It was a great day. Felt like I'm capable of getting someone out.
"First day I've thrown a ball and could see some action on it. So I'm pretty pumped. That's the first time I've had that feeling since May 14 [when he got injured]."
Niemann said late August would be a reasonable projected date for his return.