Bell has been on the physically unable to perform list since the beginning of camp after undergoing procedures on his knee and Achilles in January.
''It was just a nagging injury that had to get done,'' Bell said. ''Luckily, we were able to catch it before it got worse.''
Although Bell has not practiced with his teammates, he still thinks he'll be ready in time for the start of the regular season.
''After speaking to the doctors back in June, they told me that if I'm running at all by the end of July, I'm making good progress and by the end of July, I was running,'' Bell said. ''I'm not going to say I'm ready to go out there and take every play and run every down right now, but you never know how I'll feel in two weeks.''
Defensive tackle Haloti Ngata also remains out, on the non-football injury list with a hamstring problem.
''There's always that possibility that they could start,'' Lions coach Jim Caldwell said of Bell and Ngata. ''There's also a possibility that they could both be activated here shortly. It just kind of depends on their progression, but they're moving along really well, I can tell you that.''
Bell said he agreed with Caldwell that he was getting closer, which is why he isn't feeling frustrated.
''If I wasn't making any progress, I'd be frustrated,'' Bell said. ''But I see my young bucks out there, my young bulls out there, and that goes as far as my O-line, our new O-linemen that we have in, also the new running backs, they're doing an amazing job. I'm really proud of them.
''I've seen the growth from the time they got here to where they are now, I think we'll have an explosive running game this year.''
Abdullah, the Lions' second-round draft pick, has 12 carries for 82 yards in three games.
Zenner, an undrafted rookie free agent out of South Dakota State, has impressed with 25 carries for 162 yards and one touchdown in three games.
Bell had 223 carries for 860 yards and seven touchdowns, and 34 receptions for 322 yards and one touchdown last season.
The Lions ranked 28th in rushing last season with Bell and an injured Reggie Bush.
Bell expects that to improve, especially once he's healthy.
''I'm seeing things this preseason with things opening up that brings a smile to my face,'' Bell said. ''Makes it more interesting to be back, but at the same time be smart. Everybody knows that this season, it's a marathon, not a sprint, so gotta be smart about my return.''
NOTES: LB Kyle Van Noy, who has an undisclosed injury, doesn't expect to start the season on the physically unable to perform list. ''I don't think it'll cost me a half a season. That's for sure,'' Van Noy said. ''It's week to week.'' ... Teams have to cut their roster to 75 players by 4 p.m. Tuesday, which can be difficult for the coaches as well as the players. ''Sad day, to be honest with you,'' Caldwell said. ''These are guys that have hopes and dreams, families involved, so it's not just one of those things. It's tough on these guys, and a difficult situation. It's not one of these things that we're flippant about it.''
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