Newport Gwent Dragons: Carl Meyer and Pat Howard ruled out of Worcester game
Newport Gwent Dragons full-back Carl Meyer and wing Pat Howard will miss Saturday's European Challenge Cup tie at Worcester.
Both took blows to the head in the Pro12 defeat by Leinster and are undergoing a return to play protocols.
Mayer was taken off in the first half while Howard was injured in the final move of the 28-15 defeat.
"Carl is not going to be included. Yesterday he was having symptoms and he's been ruled out," said Jones.
"Pat's coming on okay. He hasn't been able to take any part in anything and probably wouldn't even be able to push at him if he'd be able to do a team run and we don't want to do that with him."
Dragons have back-to-back matches against Worcester followed by Welsh derbies against Cardiff Blues on Boxing Day and Ospreys on New Year's Day.
"We've got five huge games coming up," added Jones.
"Obviously this one against Worcester then Worcester again then the derbies and then Treviso at home.
"They're huge games for us so we have to be careful what we do with our squad."
The Dragons have added to their squad by signing forward Robson Blake from National Championship club Bedwas.
The 21-year-old has played for Dragons Premiership Select in the British and Irish Cup in 2015-16.
Blake made his regional debut in the Dragons' Anglo-Welsh Cup defeat at Leicester and has also played in the British and Irish Cup matches against Bedford and Ealing.
He has signed a dual deal between the Bridge Field and Rodney Parade sides that will become a professional contract with the Dragons next season.