The only question is whether erstwhile starter Jeff Garcia will be healthy enough to fill the backup role or whether he'll be wearing a ball cap as the No. 3 quarterback.
The quarterback position has been the subject of turmoil and controversy since the Lions got off to a stumbling start, with Harrington starting the first five games, Garcia recovering from a broken leg and sprained ankle to start the next two games, and Harrington returning to the starting job for the eighth game when Garcia was sidelined by additional injuries to his leg.
Harrington is 2-4 as the starter, Garcia is 1-1. And the Lions are still struggling to make a run at the Chicago Bears in the NFC North before it's entirely too late.
If there is any encouraging sign for the Lions as the go into the second half of the season, it is the fact that several of their injured top-line players - and one suspended player - are ready to return to action.
Among those expected back this week are Pro Bowl defensive tackle Shaun Rogers, wide receiver Roy Williams and wide receiver Charles Rogers, who missed four games on a drug suspension and a fifth game because coaches felt he wasn't adequately prepared after his first week back in practice.
In addition, Pro Bowl cornerback Dre' Bly began practicing this week with a cast on his right wrist and might be ready to play against Atlanta on Thanksgiving Day.
Meanwhile, Harrington will try to keep the Lions in the race with a win against Arizona. He struggled in the first half of the season, completing only 54.5 percent of his passes with five touchdowns, 10 interceptions and a passer rating of 57.5.
"We have to start small right now," said Harrington on Friday. "I don't say this to be smart, but we have to set the most minimal goal right now which is run the football and throw the ball well.
"We need to do the little things we can on offense to get something rolling, to get something going so we can win a football game. That is our goal right now, to win this football game."
"It's feeling better each day," he said. "I can feel improvement, especially over the way I felt last week. I'm doing a lot more this week than I did last week, so I think if I can continue in that sort of position, I'll be ready to be the No. 2 guy on Sunday."