Seiichi Uchikawa was taken off the active roster today with an avulsion fracture in his left thumb. He suffered the injury while playing first base in the eighth inning of a game against the Chiba Lotte Marines at YafuOku Dome on July 23. He was examined at a hospital in Sendai (MRI, CT scan) on July 25 and diagnosed with an avulsion fracture in the ulnar base of the proximal phalanx. He will most likely require about six weeks for a full recovery.
[UPDATE 8/8 @ 9:31pm]
The media learned on August 7 that Uchikawa might not be able to return to the active roster before the end of the season. The six week window was apparently how long he needed to keep his thumb immobile. The actual window might be more like eight to twelve weeks.
Source: Daily Sports 8/8/2017
[UPDATE 9/5 @ 3:27pm]
Uchikawa is still unable to swing the bat. He is playing light games of catch and taking easy fielding practice.
Source: Nikkan Sports 9/5/2017
[UPDATE 9/9 @ 12:02am]
Uchikawa’s cast was removed on September 5. He used a tennis ball for soft-toss batting and light fielding practice on September 6. He moved up to a hard ball for soft-toss batting practice on September 7 and took about fifty swings. Assuming no major setbacks, he could start taking batting practice against a pitching machine on September 20. There is a chance he might be able to return to the active roster in early-October.
[UPDATE 9/18 @ 4:02pm]
Uchikawa might be ready to play in rehab games some time this week. He participated in pennant celebrations on September 16 and worked out at Seibu 2 Stadium on September 17.
Source: Nikkan Sports 9/18/2017
[UPDATE 9/21 @ 4:53pm]
Uchikawa could return to the active roster in time for a game against the Rakuten Eagles at YafuOku Dome on September 25. He worked out for about two hours at the Chikugo facilities on September 20. He is slated to join the Ni-gun team on September 22 and will play in rehab games as a designated hitter on September 23 and 24 against Hanshin.
Source: Nikkan Sports 9/21/2017
[UPDATE 9/23 @ 10:41pm]
Uchikawa started at designated hitter and batted fourth against Ni-gun Hanshin today. He went 0-for-2: line out to third, fly out to right. He was removed from the game in the fourth inning.
[UPDATE 9/24 @ 3:46pm]
Assuming no setbacks, Uchikawa will remain at Ni-gun until at least September 28. From there, he could join the Ichi-gun team in time for an Orix game on September 30.
Source: Sponichi 9/24/2017
[UPDATE 9/25 @ 1:22am]
Uchikawa played in another Ni-gun rehab game on September 24. He went 2-for-4 (single to center in the second and single to right in the eighth) against Hanshin.
Source: Nikkan Sports 9/24/2017
[UPDATE 9/27 @ 10:47pm]
Uchikawa got the start at designated hitter and batted fourth against Ni-gun Chunichi earlier today. He went 1-for-3: strikeout looking, ground out to short, double to left-center.
Source: Sports Hochi 9/27/2017
[UPDATE 9/28 @ 9:36pm]
Uchikawa is still set to return to the active roster in time for an Orix game at Kyocera Dome on September 30.
Uchikawa played in a Ni-gun game against Chunichi at Tama Home Stadium Chikugo on September 27. He got the start at designated hitter and went 1-for-3 with a double. He was slated to play some defense, but was moved to designated hitter because field conditions were not ideal.
Source: Nikkan Sports 9/28/2017
[UPDATE 9/29 @ 12:18am]
Uchikawa got the start a first and batted fourth during a Ni-gun game against Chunichi on September 28. He went 1-for-3: Ks, 1B7, F8. He was scheduled to play until the fifth, but asked for another at bat and remained in the game until the sixth.
Added additional information from game on 9/30 @ 12:50am.