Mikel Leshoure took team RB reps for the fourth straight workout Thursday, continuing his progression toward making his NFL debut Saturday vs. Oakland. Meanwhile, fellow RB Jahvid Best remains on PUP with concussion symptoms.

If Best is sidelined through the end of camp, Detroit will have the option of placing him on the regular season PUP list. That roster distinction would give Best an additional six weeks to recover before the Lions would have to make a final decision on his status. Although all signs point to Best being placed on PUP, Jim Schwartz said Thursday that no decision has been made regarding his health.

Best's injury issues have gone from problematic to downright perplexing. He hasn't cleared a contact concussion test since Week 6 of the 2011 season, yet both Best and Lions coach Jim Schwartz say the third-year player is in good health. “[Best] is doing great,” Schwartz said. “He’s working out hard. He’s just not cleared [for contact] yet.”

Best has expressed similar sentiments, saying he's “working hard” to pass his concussion testing. That assertion is puzzling, however, since there doesn't appear to be a specific workout regimen designed to improve players' chances of passing a contact test. It seems that the only clear course of action for Best and the Lions is to wait and see if his condition improves.

WR Osgood happy to be in Detroit: Special teams ace Kassim Osgood was faced with an unfamiliar situation during the 2012 offseason after he was released by an NFL team for the first time in his career. After waiting five months to return to professional football, Osgood, 32, says he's “blessed” to have a chance to make the Lions' roster. "When you get late in your years, and you get those small opportunities, you got to come and make the most of it,” he said. Osgood is eligible to play against the Raiders on Saturday, but he said he doesn't expect to see game action. His arrival is part of the Lions' attempt to find a more consistent special teams unit, and Jim Schwartz praised the kick coverage specialist's skill. “[Osgood] has played about everywhere on kickoff coverage," Schwartz said. "He’s a guy that traditionally has been double-teamed. He’s a four-phase [kickoff and punt coverage and returns] special teams guy.”

It's likely that the Lions didn't bring a player with Osgood's experience into camp to cut him nine days later. He's a good bet to take one of the Lions' final two WR roster spots alongside Ryan Broyles, Calvin Johnson, Nate Burleson and Titus Young. That should leave Patrick Edwards, Dominique Curry and Nate Hughes battling for the remaining spot. In that scenario, Hughes' time in Detroit last season could give him an edge.

Vanden Bosch unlikely to play vs. Raiders: After participating fully in Detroit's Wednesday practice, DE Kyle Vanden Bosch was limited to individual drills during Thursday's workout. The reduced workload indicates that he will miss Detroit's third preseason game Saturday night. He has yet to appear in a preseason game after injuring his knee in the week before Detroit's preseason opener. Vanden Bosch's intense training regimen makes it less important that he participate in preseason games, but his inability to complete practices is a concern. If he isn't healthy by Week 1 of the regular season, expect DEs Willie Young and Lawrence Jackson to split time as his replacement.

QB R.J. Archer's release opens door for Moore: By releasing QB R.J. Archer on Thursday, Detroit ended any possible competition over who will be the team's third QB. The job now belongs to Kellen Moore -- provided the Lions choose to keep three QBs on the roster. Moore's average arm strength is still an issue, but Lions coaches seem willing to give him every opportunity to prove his worth. “[Moore] adapts very quickly,” Jim Schwartz said. “You saw improvement from him from [preseason] Game 1 to Game 2, and he needs to stay on that same path...He’s starting to get into a little bit of rhythm, and he had a good day [Thursday].”

Injury notes: LB Travis Lewis (quad), KR Stefan Logan (ankle), WR Ryan Broyles (ACL) and S Louis Delmas (knee) did not participate in Thursday's practice. Broyles participated in team drills earlier this week. It's unclear what impact his limited participation will have on his availability Saturday vs. Oakland.

Follow Lions reporter John Kreger on Twitter at @CBSSportsNFLDET and @JohnKreger.