"I have no comp."
Joey Votto is a human, even if his numbers suggest otherwise. Unfortunately, it's still pretty hard to predict how long humans will take to recover from injuries. After a setback earlier this month, Joey is now on track to return Saturday, September 1st (no roster move will be necessary then) - though that's subject to change.
Votto originally injured his knee on June 29th, then re-injured (or maybe further injured it) on July 16 and had surgery the next day. His original ETA was 3-4 weeks, but if he returns Friday, it will have been just over 6 weeks since he's played in the majors. That's not too surprising, given the history of similar players with similar injuries. And also the history of teams generally playing low-ball with injury estimates.
Now that we know about how long he will have been out, what can we expect when he returns? I pulled a few recent examples of similar players (relatively speaking) - mostly 1B - with similar injuries to see how they fared on their return. I'm not sure how instructive this is - given that it's a small sample and Joey is a pretty singular player - but it should satisfy some level of curiosity. Probably a level that shouldn't be there.
Berkman was the most obvious comp:
Lance Berkman, 2005-present
First, a horrible turn of phrase: Lance Berkman has gone under the knife more times than a fork at a utensil stacking contest!
The Puma had surgery on his right knee in November 2004 after tearing his ACL playing flag football at a church function in the offseason (and then a surgery to remove scar tissue from that surgery in 2005). While it wasn't his meniscus that time, he was a late-20-something baseball-mashing 1B with a knee injury. Berkman wound up posting the second-best OPS+ of his career in '06, but but not before sitting on the DL though April 2005 and slumping through his first month back.
Berkman's latter surgeries might be less comparable due to age and injury history. He didn't start the 2010 season until April 20th due to surgery and, though he showed some early power, slumped through much of the first month in what proved to be an off year.
Berkman's 2012 meniscus surgery on his left knee might be the most relevant, but he's 8 years and several surgeries ahead of Votto. Votto is also arguably in much better shape than Berkman was at the same age. Berkamn has posted good numbers over the whole of 2012, but hasn't hit for any real power since returning from surgery (though he did hit the DL again).
Having injured both knees as a switch hitter, all of Berkman's injuries have affected the push-off portion of his swing, as Votto's left knee injury may. If there's anything to be gleaned here, it's that there may well be a period of roughly a month when power derived from the legs is sapped and it's hard to turn on a ball. I'm encouraged by Berkman's example in the long-term, especially comparing with Joey's physique and age advantage.
Todd Helton, 2008
In 2008, Helton was out from July 3rd to September 12th with a cartilage injury in his lower back. This example isn't that helpful, but Helton - like Berkman - had a power outage for about a month after returning from his injury. And the injury involves cartilage - what I like to call "body jello." Also, the lower body. And Helton is a 1B.
Rafael Palmeiro, 1999
I'm hesitant to use this example. Palmeiro game back after less than a month from meniscus surgery in 1999, after being projected out at least 4 weeks. He hit for more power in '99 than he ever did and plenty in his first month back. It may have been the fact that it was on his non-push-off knee or maybe the fact that he was probably injecting alien stem cell ectoplasm into his body.
David Ortiz, 2007
Ortiz, a lefty, had off-season surgery on his right knee in November 2007. His power was diminished in 2008.
Miguel Montero, 2010
Montero hit the DL with a meniscus tear in his right knee in April 2010. He was out 7 weeks, but returned en fuego over his first month. Montero bats lefty.
Chris Coghlan, 2010
Following his 2009 ROY season, Coghlan hit the DL the next July. He missed the rest of the season. Coughlan injured his left knee as a lefty, but his free-fall since his sophomore slump started over 3 months before his knee injury.
Chipper Jones, 2012
Jones, like Berkman, switch hits and injured the meniscus in his left knee this year, but continued to hit for power at an even more advanced age. He hits for a little less power from the left side. This an encouraging example, though Jones' surgery was less extensive and didn't suffer from complications.
There will be some more contemporary examples when players like Victor Martinez and Matt Gamel return. If this is anything besides a dig through the archives, it's may show that injuries to a slugger's lower body, especially to the back knee in the swing, can put a temporary damper on power.
I'd predict Votto's return numbers with zero confidence, but the Reds shouldn't expect the old Joey right out of the gates. Which makes the Todd Frazier Fail Safe that much more valuable.