The Jets held their 18th and final practice of training camp on Wednesday morning ahead of Friday night's preseason game against the Giants.
All week, quarterback Sam Darnold worked with the starting offense against the scout-team defense. So it's pretty clear what is happening here: The Jets are getting Darnold ready to start in that third preseason game against the Giants.
That game is typically the final dress rehearsal for players who will start in Week 1, so it's safe to assume that if Darnold plays well enough against the Giants, he probably will start in Week 1 at the Lions.