Welsh defender Matthews was subbed out of the Bhoys' 3-1 win at Heart of Midlothian on Saturday after injuring his ankle whilst young winger Forrest has an ongoing back problem but Lennon hopes both are fit for Wednesday night's first group match.
"Adam is fine. He just jarred his ankle and couldn't continue but we are hoping he will be okay for Wednesday. It is just a twist," said Lennon.
"James Forrest, with his sciatica problem, we are hoping he will be okay to travel and be fit and available.
"Thankfully, apart from that, we have a clean bill of health.
"The only loss, and it was a big one, was Steven Mouyokolo with an Achilles injury during the week."