The visit of Serbia to Windsor Park is pivotal to Worthington's hopes of securing second spot in Group C and calf injuries to both players have given him a serious headache.
Rangers striker Lafferty would be a certain starter after missing the 4-0 win over the Faroe Islands with a hernia problem, while Celtic playmaker McCourt lit up that game with a man-of-the-match performance and two memorable goals.
Worthington refused to rule the pair out but conceded that the outlook was not positive.
"Time is starting to catch up with them a little bit but we'll carry on working with them on a continuous basis and see where we're at," he said.
"The injury situation with them is becoming a little bit difficult but we'll have to see.
"It's an unfortunate situation that the two boys have picked up these knocks and with 24 hours to go time is getting tight. At this moment in time it's all ifs, buts and maybes."
With Derby's Jamie Ward already ruled out of the original 23-man squad, Worthington could be left short of attacking options.
In Lafferty's absence he would be likely to start with record scorer David Healy up front, despite his lack of playing time at Rangers and no international goals since October 2008.
Millwall's Josh McQuoid and Plymouth's Warren Feeney are also on duty, with Chris Brunt back from suspension to offer a creative option from midfield.
Northern Ireland go into the game one point ahead of Serbia in third place but are in no doubt about their opponents' quality.
Vladimir Petrovic's side came from behind to win the reverse fixture in Belgrade 2-1 and boast a number of high-profile players such as Dejan Stankovic, Branislav Ivanovic, Milan Jovanovic and Zoran Tosic in their ranks.
While three of the major stars - Manchester United captain Nemanja Vidic, Juventus' Milos Krasic and Birmingham forward Nikola Zigic - are all absent for this match, Worthington expects the toughest of tests.
"We know the quality Serbia as a group possess, their quality is proven if you look at the clubs they are at throughout Europe," he said.
"There is a lot of ability there, a lot pace, a lot of strength.
"They're in a very fortunate situation that if they lose a good player or take a player off for whatever reason, they can bring a player as good or even better on.
"More often than not if we take a player off we're sticking a younger one in.
"They've got a strong pool of players and it's about how you deal with that.
"But we have to match them, which we are capable of doing.
"We proved for 45 minutes in Belgrade that we are capable of doing that."