Ryan is ready to make his Racing return for their trip to Belfast
Donnacha Ryan could return to the Racing 92 pack for their pivotal Champions Cup visit to Belfast on Saturday (3.15pm), but the Parisians will be without France stars Teddy Thomas, Cedate Gomes Sa and Camille Chat.
The trio have also been left out of the France squad for the upcoming Six Nations. Chat suffered a shoulder injury in November, while Thomas picked up an injury in last weekend's win over Toulon.
Speculation suggests Thomas will be replaced by fellow France international Brice Dulin which may see Simon Zebo switch to the wing, having played most of his rugby at full-back.
A knee cartilage problem has kept Ryan out of action for six weeks but he looks set to make a timely comeback for the battle with some familiar faces. The Tipperary native is rumoured to be on the cusp of signing a new deal to remain with Racing, having made a big impact since arriving in 2017.
He and Zebo will relish the chance to shine in front of an Irish crowd in a high-stakes game.
Racing's challenge will be weakened by the absence of Chat and Gomes Sa who are part of a formidable, all-international front-row unit with Eddy Ben Arous.
Racing bullied Ulster's scrum in the reverse fixture, but Dan McFarland's men have made big improvements in that area.
The French side lead Pool 4 by five points from Ulster and can book their place in the quarter-finals with an away win.
The northern province can keep their last-eight hopes alive with victory or even a losing bonus point after back-to-back wins over Scarlets ignited their campaign.
France coach Jacques Brunel has included five new faces in his squad for the Six Nations, which kicks off in four weeks' time.
Montpellier's South African lock Paul Willemse is called up, having secured a French passport, while the Toulouse trio of Dorian Aldegheri, Thomas Ramos and Romain Ntamack, and Brive prop Demba Bamba, are included.
There is no place for Yoann Maestri or Paul Gabrillagues, while Morgan Parra is recalled along with Gael Fickou.