West Brom boss Tony Mowbray says the number of injuries at the club has reached a 'critical' level.
"Our injury problems are getting worse," Mowbray told his club's official website.
"Jonno has gone off with a medial knee ligament injury and, until we get a scan, it's hard to say how long he will be missing.
"I would suggest, even if it's a grade one injury, he will be at least two to two-and-a-half weeks out.
"Ryan has gone off with tired muscles around his groin. If you add him to the centre-halves we've already got out in (Leon) Barnett, (Jonas) Olsson and (Abdoulaye) Meite, and all the others, the list keeps growing - and it's not good.
"I'm pretty sure we're not the only club suffering injuries but it's coming to the critical point for us."