Ulster have confirmed that wing Jacob Stockdale remains an injury concern for the Pro14 quarter-final with Connacht at Kingspan Stadium on Saturday 4 May.
On Monday Ulster head coach Dan McFarland said there are "definitely fears" over Stockdale's fitness.
Last week Ulster said that Stockdale was being "monitored on an ongoing basis" after suffering a hamstring injury in their win over Edinburgh.
Ulster are hopeful that skipper Rory Best will be fit to face Connacht.
Hooker Best suffered an ankle injury in the Irish province's Champions Cup quarter-final defeat by Leinster in Dublin on 30 March.
Best has subsequently announced that he will retire from playing after the World Cup in the autumn so the game against Connacht would be his last as an Ulster player at Kingspan Stadium should he be deemed fit to play.
Both Ulster and Leinster are expected to field much-changed line-ups for this Saturday's interprovincial derby in Belfast, the final regular Pro14 game of the season for both sides.
Ulster are already assured of a second-placed finish in Conference B, behind runaway leaders Leinster, who have secured home advantage for the semi-final stage of the play-offs.
Long-serving Ulster centre Darren Cave is expected to captain the side on Saturday as he prepares to hang up his boots at the end of the season.
McFarland must plan without utility back Will Addison and prop Marty Moore for the remainder of the campaign as both have been ruled out through injuries.
Leinster's Adam Byrne will miss the rest of the season having picked up a quad injury against Glasgow Warriors while Sean Cronin is unavailable for selection this weekend after he sustained a calf injury in Sunday's Champions Cup semi-final win over Toulouse.
Rhys Ruddock has re-entered the Graduated Return to Play protocols after feeling unwell following the captain's run on Saturday and therefore will not be available for selection this week.
Ross Molony is progressing well from a back injury. Andrew Porter (pectoral) and Jamison Gibson-Park (hamstring) both missed the win over Toulouse and will be further assessed this week before a decision is made on their availability for this weekend.
Leinster captain Johnny Sexton and Rory O'Loughlin both came through the weekend with no issues and will continue training as normal this week.