However, that doesn't mean he's not wanted.
The Lions traded a seventh-round pick to the 49ers to acquire him, and Lions coach Jim Schwartz is quite happy to have the veteran ready in case something happens to second-year starter Matt Stafford.
"We're very comfortable with Shaun," Schwartz said Tuesday. "He's a guy who has been in the league for several years, and who can do the job that we need. He's proven that throughout his time with us."
Hill, meanwhile, was making six starts for the 49ers, winning three — one more game than the Lions have won in the past two seasons combined.
Hill's throwing motion — a three-quarters, short-armed toss — isn't typical, but Schwartz doesn't care.
"It may not be pretty, but it works for him," Schwartz said. "He's a little bit of a gunslinger, and it never looks the same way twice, but he's a very accurate passer, which is what we want. It doesn't have to look beautiful if he's getting the ball to the receivers."
Hill's oddball motion came as a result of a broken index finger, which caused him to alter his follow-through, and years of running the scout team offense in Minnesota.
"It's a big old mess now," he said. "In practices, you are usually facing a lot of pass rush without much time to throw, so you develop a lot of quick deliveries and sidearm throws just to get the ball around guys."
Hill has no illusions about his role — he wasn't brought in to compete with Stafford for the starting job, and once the regular season starts, he'll have to be ready to step in despite limited playing time.
"During the regular season, you aren't getting any reps, so your preparation has to be mental," he said. "I don't want to be a backup, but I know that's my role on this team, so I have to be keep improving and stay ready to play if they need me."
Hill practiced Tuesday morning, but did not take part in the afternoon session.