Cabrera's only start this season was at second base against St. Louis on Wednesday, when he went 0-for-2. He entered the game against the Red Sox on Saturday as a pinch-runner and later singled in the 10th inning of the Reds' 6-4 loss.
Janish, a defensive specialist, is hitless in his past 11 at-bats and is 1-for-22 in his past eight games. He has started the past five games at shortstop after Jerry Hairston went to the disabled list with a fractured left thumb.
Janish struck out four times in the series opener against the Red Sox on Friday and was 0-for-3 with a walk on Saturday, when Boston sent knuckleballer Tim Wakefield to the mound. It was only the third time Janish had faced a knuckleball pitcher on any level.
"The reports were that he needed to improve his offense," Baker said. "He went to Triple-A and was vastly improved, but we had to call him here out of necessity, when in reality you'd have liked to see him stay there and improve some more over a longer period of time."
The Reds have cycled through shortstops this season, and Janish is No. 4. Cincinnati's other three shortstops -- Alex Gonzalez, Jeff Keppinger and Hairston -- are all on the disabled list. Janish was called up from Triple-A Louisville on May 14 to fill the roster spot vacated by Keppinger.
"We lost Gonzalez, Keppinger and Hairston -- how many teams that lose three shortstops have four that you can put in there?" Baker said. "I don't know many. And still, even at the Triple-A level, where you can go get somebody. Usually when you lose that many, you've got to go to the Double-A or [Class A] level or you've got to trade for somebody."
Baker said he still has faith in Janish, who hit .293 at Louisville this season before his callup.
"It's too early to label him with what he can do and what he can't do," Baker said. "That's because we're impatient. We're a lot more impatient now and we're more oriented to winning now as opposed to trying to develop somebody. If he's not hitting, we're supposed to get him out and get another guy in. That's not right, but that's how it is.
"There are a bunch of guys who came up here and struggled early, and some of them are in the Hall of Fame. Ozzie Smith struggled, but he learned how to do it."