Answer based on context:

Coming off a season-sweeping road win over the Jets, the Bills went home for a Week 9 intraconference duel with the Cincinnati Bengals.  with rookie QB Trent Edwards out for a sore right wrist, J. P. Losman got the chance to reclaim his starting job. In the first quarter, Buffalo drew first blood with Losman completing an 8-yard TD pass to WR Lee Evans that was initially ruled incomplete.  The Bengals would respond with QB Carson Palmer completing a 15-yard TD pass to WR T. J. Houshmandzadeh.  In the second quarter, the Bills went back into the lead with kicker Rian Lindell getting a 23-yard field goal.  However, Cincinnati immediately responded with WR/KR Glenn Holt returning the kickoff 100 yards for a touchdown.  Buffalo ended the half with Lindell kicking a 21-yard field goal. In the third quarter, the Bills went back to work with Lindell getting a 21-yard field goal.  However, the Bengals answered with Palmer completing a 1-yard TD pass to FB Jeremi Johnson.  Fortunatenly, in the fourth quarter, Buffalo began its final assault with Lindell nailing a 38-yard field goal.  Afterwards, rookie RB Marshawn Lynch was a key player as he threw an 8-yard TD pass to TE Robert Royal on a trick play, along with getting his best run of the year with a 56-yard TD run. With the win, not only did the Bills improve to 4-4, but they have won three-straight games for the first time since 2004. Losman ended the day completing 24 out of 34 passes for 295 yards with a touchdown and an interception.  Meanwhile, Lynch finally managed to get not only his first 100-yard game, but also his first 150-yard game.  He ended the day with 29 carries for 153 yards and a touchdown, along with his touchdown pass.

How many yards was Rian Lindell's shortest field goal?
21