The Fir Park coach looked on in anguish as long-term club captain Stephen Craigan retired while versatile stopper Tim Clancy knocked back a new deal and is set for a summer move to Hibs.
McCall's mood was lifted when left-back Stevie Hammell, and the man who will succeed Craigan as skipper, Keith Lasley, both agreed two-year deals.
But with McCall set for showdown talks with Jennings and his agent in Merseyside on Friday, McCall admits that D-day for his summer plans is looming.
The Well boss said: "Really what happens with Stevie will dictate just what we can do in terms of players coming in to the club.
"Right now, with Craggs retiring and Tim declining the new deal we tabled him, we need to bring in another centre-back and preferably one with experience.
"Should Jenno go then that would leave us a bit light in midfield as well. I will be having talks with him and his agent down in Merseyside on Friday and my hope is that we can have things resolved then, but realistically it could drag on for a good while yet.
"But at the moment the priority remains signing a centre-back."
However, SportTimes understands that the Well midfielder will not be entertaining any interest from League Two side Rotherham United who had sounded out the midfielder over a move to Yorkshire.
But McCall remains upbeat that the re-signing of Las could swing the balance in his side's favour in their bid to keep hold of Jennings.
The Well gaffer said: "Obviously Las and Jenno have formed a very good partnership over the last three seasons and the chance to play alongside Las in the Champions League qualifiers has hopefully got to be attractive to Stevie.
"We know that we maybe can't match the money being tabled, even by sides like Rotherham, but we can certainly offer something in football terms that he would prize above that."
Meanwhile, reserve keeper Lee Hollis will pen a new one-year deal at Fir Park today and McCall believes he can push Darren Randolph all the way in the battle for the Fir Park gloves next term.
He said: "Lee really impressed me last season. He maybe did not get as much game time as he would have hoped, but every time he did he did a good job."