Herrera is recovering from a torn anterior cruciate ligament suffered Nov. 21 last year.
"We'll probably have to make a decision after that third preseason game what direction we want to go, whether or not we want to try to play him or just put him on PUP [physically unable to perform], but we'll see how he progresses," Frazier said.
Herrera is still doing conditioning as part of his rehabilitation, but he has been on the PUP list since the start of training camp. During training camp, a player can come off the PUP list whenever he is ready, but once a player starts the regular season on the PUP, he isn't eligible to play for six weeks.
The Vikings also have a couple potential starters whose status is still undetermined for Saturday's game at Tennessee.
Tyrell Johnson, who entered camp in a competition for a starting spot at safety, suffered a hamstring injury last week and hasn't practiced at all this week. Tight end Visanthe Shiancoe suffered his hamstring injury after catching a pass from Donovan McNabb in Monday's practice.
Head coach Leslie Frazier classified their injuries as "mild."
"They both should be fine. Tyrell may be [will] practice a little tomorrow. Visanthe, his is a little [more recent] than Tyrell's, so probably give him another day or so," Frazier said. "But Tyrell, I think he's going to give it a try tomorrow, see how it feels."
Frazier said they would be "very cautious" with Shiancoe.
Healthy starters aren't expected to get much playing time Saturday night, either. The coaching staff will discuss playing time Tuesday night and has a set number of plays they want to get their starters. However, they aren't expected to go above the normal protocol for Week 1 of the preseason, despite a new offense.
"I don't think so. We want to get Donovan and some of the guys some rest, but at the same time we've got three games after this one," Frazier said. "We want to get the timing down, but I think we have enough to get the legs under them a little bit, but we don't have to play a half or play two quarters or play a quarter and a half right now. We've got time."
The offense has looked uneven throughout the first eight days of training camp, but Frazier isn't pushing the panic button.
"We'd like for it to come together on Sept. 11 at … whatever time we're playing that game," Frazier said. "We'd be very pleased if it happened on that day. 3 p.m. Central? Doesn't have to happen any sooner than that and I'll be satisfied. I think we all would be satisfied."
Tim Yotter is the publisher of Viking Update. Follow Viking Update on Twitter and discuss this topic on our message boards. To become a subscriber to the Viking Update web site or magazine, click here.