The England scrum-half has been excluded from the Six Nations following his arrest for drink driving in the early hours of New Year's Day.
That was Care's second alcohol-related incident in the space of three weeks, having been arrested and fined by police for being drunk and disorderly on December 10.
England coach Stuart Lancaster told Care he would not be considered for international honours until he could prove he was trustworthy again.
Care, who said he was "devastated" by the incident, will plead guilty when he appears in court on January 16. His reaction was both humble and determined.
"I will do everything to learn my lesson and come back stronger," he said on Twitter.
The 25-year-old was backed to do exactly that by Lancaster, who said: "Hopefully it will give him the kickstart he needs to become what I believe will be world class."
Care's first chance to impress comes against a resurgent Northampton side at Franklin's Gardens.
After a stuttering start to the season, the Saints have won six of their last seven in the Premiership and last week's bonus-point win at Newcastle shot them from sixth to third place.
Northampton boss Jim Mallinder has urged his men to keep their foot on the gas against table-topping Harlequins.
"We were really disappointed earlier in the season when we went down to Quins. We didn't play well at all, they did and deservedly won the game," he said.
"They are a tough side to beat and we have to concentrate on our own game and maintaining our performance for a full 80 minutes.
"We've been building a little bit of momentum of late and while we were a bit frustrated by some of our European form, winning against Castres and Bath at home and then picking up a bonus-point at Newcastle last week shows we are in good form and hopefully we can carry that into this Friday's game."
Care was man of the match for Harlequins in their victory over Exeter on New Year's Eve and he starts in an unchanged back division, with Rory Clegg continuing at fly-half in the absence of Nick Evans.
Up front Harlequins restore hooker Chris Brooker and prop James Johnston to the front row while Olly Kohn returns from injury to partner George Robson in the second row and Nick Easter starts at number eight.
Chris Ashton, who has been linked with a summer move away from Northampton, returns from suspension to the Saints starting line-up.
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