Ibrox manager Ally McCoist revealed the Northern Ireland international would be leaving the club's German training camp early to see a specialist.
It is unclear how long Lafferty will be out for but Rangers expect him to miss a "number of weeks".
McCoist told the club's official website: "It was a little bit disturbing last night when we learned that Kyle has a problem with his groin.
"The doctors and the physios had a look at him and decided it was a niggle that wasn't going to clear up over here.
"So we have decided to send Kyle home tomorrow and he is down to see a specialist on Tuesday to try to get to the bottom of the problem.
"We will know better when we get back from Germany but it is a little concerning."
The injury is a major blow as Lafferty, 23, finished last season on top form for the second year running, hitting a hat-trick in the title-clinching victory at Kilmarnock.
McCoist has so far drawn a blank in his search to bring in a striker with a bid for Dundee United's David Goodwillie turned down, although David Healy recently signed a new contract.
The Rangers manager said of Lafferty: "It's a big disappointment for him and it's a big disappointment for us because he and Nikica (Jelavic) finished the season so well and we were hopeful they would start the season in fine form.
"However, that does not look like the case with Kyle having this niggle."
Meanwhile, McCoist admitted he needed reinforcements after his side's 3-0 defeat by Bochum - the second loss of their German tour without scoring.
"I don't like losing any game and the disappointing thing was the standard of goal that we lost," said McCoist, who again started with his only summer signing, Juan Manuel Ortiz.
"In terms of the overall game I felt we were fine for 60 minutes or so. We had a chance to go one up through Nikica but the goalkeeper made a good save and then we lost a goal straight away.
"It's another 90 minutes for the boys and we are only 12 days into our pre-season.
"We definitely need to get one or two fresh faces in to help the lads and we will do that.
"So it was disappointing to lose but we are certainly not too downbeat."
As well as Lafferty, McCoist was without Madjid Bougherra and David Healy, with the latter suffering a minor ankle injury.
McCoist would not take a chance on Bougherra, whose future remains the subject of speculation as he enters the final year of his contract.
McCoist said: "He was feeling his hamstring a little bit at training this morning so we decided not to risk him.
"The important thing is to have Madjid fit and ready for when we start our league campaign.
"We have not had an offer for him. He is a Rangers player and the one thing about Madjid is that he gives his all in every game, and I have no doubts that he will do that again.
"We are looking to strengthen a few areas and the defence is one of them."