Amaro was running a route over the middle during an offense-only, non-contact drill when he suddenly stopped and reached for his lower back. He came off the field and eventually headed back to the locker room.
"I don't know much right now," Jets head coach Todd Bowles said. "They told me he's sore, but I'll find out more after this."
Defensive lineman Sheldon Richardson was not present Wednesday. Richardson has only attended some of the Jets' OTAs, which are technically voluntary, but Bowles sounded optimistic that Richardson will participate in the team's mandatory minicamp next week.
A bigger question mark for next week is fellow D-lineman Muhammad Wilkerson, who has skipped the entire offseason program thus far, desiring a contract extension.
"It’s mandatory, but that’s up to Muhammad," Bowles said, "and I don’t know what the answer to that question will be until next week."
Given that everything Wilkerson has missed so far was voluntary, Bowles said Wilkerson would line up with the starters if he does show up next week. Bowles is implementing a new system, but the coach said Wilkerson has an iPad with the playbook installed on it.
"Will he grasp everything in the first three days? Probably not," Bowles said. "But he’ll have a good grasp of the things that we’re putting in to make him comfortable."
Running back Chris Ivory, wide receiver Jeremy Kerley and cornerback Dee Milliner were back on the field Wednesday, after missing last Wednesday's OTA -- the previous one open to the media -- for personal reasons.
Ivory and Kerley were full participants, while Milliner worked on the side as he continues to recover from a torn Achilles tendon suffered last season.
It remains to be seen whether Milliner and/or Ridley will be cleared by the start of training camp in July.