The San Francisco 49ers find themselves in a bit of a pickle on defense. The team released their Thursday practice participation report [url=http://www.49erscheapshops.com/cheap-authentic-mike-mcglinchey-jersey]Cheap Mike McGlinchey Jersey[/url] , and for the second straight day, free safety Adrian Colbert did not practice. Colbert is dealing with a hamstring injury, and his status is a big question mark for Sunday.D.J. Reed has been listed as the team’s backup free safety, even though Jimmie Ward has experience at the position. Ward played played free safety last year, but was moved to cornerback this season. Kyle Shanahan will likely offer some clues as to Sunday’s plan, but this is a big position to watch.Malcolm Smith remains sidelined with his own hamstring injury, missing a second straight practice. He was listed as doubtful last week, and it seems unlikely he plays this week. That would likely mean Elijah Lee starts at WILL, next to Fred Warner. The team signed linebacker Terence Garvin, but he is likely simply in the key reserve role at all three linebacker spots with Brock Coyle on injured reserve.The right guard position remains a real problem as well. Mike Person and Joshua Garnett both were listed as DNPs. Najee Toran has been getting first team RG snaps this week [url=http://www.49erscheapshops.com/cheap-authentic-fred-warner-jersey]Cheap Fred Warner Jersey[/url] , but Cam Inman tweeted that Person looked a little more possible than Garnett for Sunday. If Person and Garnett are inactive, it seems like Toran would start at right guard and Matt Tobin would be the primary reserve.Wide receiver Marquise Goodwin remains out with his quadricep injury. Given the speed element to his game, it would not surprise me to see him inactive this Sunday. That means keep an eye out for Dante Pettis.Here’s the full Thursday practice participation report.DNP: S Adrian Colbert (hamstring), G Joshua Garnett (toe), WR Marquise Goodwin (quadricep), G Mike Person (foot), LB Malcolm Smith (hamstring)Limited: OL Erik Magnuson (hamstring), S Jaquiski Tartt (shoulder), CB K’Waun Williams (rib), CB Ahkello Witherspoon (ankle)Full: T Joe Staley (not injury related) The injury news could have been worse regarding Matt Breida [url=http://www.49erscheapshops.com/cheap-authentic-brock-coyle-jersey]49ers Brock Coyle Jersey[/url] , but it appears the San Francisco 49ers will be without their top running back for at least one game.Breida underwent an MRI on Monday that showed a "serious sprain" to his left ankle, according to coach Kyle Shanahan. That likely will sideline Breida for next Monday night's game at Green Bay."It was positive news that it wasn't a high ankle sprain, (but) he'll probably end up being doubtful this week," Shanahan said.As the 49ers look to rebound from Sunday's deflating 28-18 home loss to the Arizona Cardinals, they'll probably have to do so without the player who's been their best offensive weapon, so far.Breida ranks fifth in the NFL with 369 rushing yards, and his 7.5 yards per carry average leads the league among those with at least 25 rushing attempts. He enjoyed a terrific first quarter Sunday before leaving with his ankle injury.Breida has been a bright spot for the struggling 49ers (1-4), who lost projected starting running back Jerick McKinnon to a torn ACL in the preseason and then watched No. 1 quarterback Jimmy Garoppolo suffer the same season-ending injury in Week 3 against Kansas City.Without Breida, the 49ers would lean heavily on veteran Alfred Morris, who has shared ball-carrying duties with Breida and is more of a between-the-tackles runner.Raheem Mostert is third on the depth chart [url=http://www.49erscheapshops.com/cheap-authentic-k_waun-williams-jersey]http://www.49erscheapshops.com/cheap-authentic-k_waun-williams-jersey[/url] , but he's more of a special-teams contributor and he fumbled his first carry Sunday after Breida left the game.It wasn't a surprise that the 49ers brought in several running backs for workouts Monday afternoon. One of them was Jeremy McNichols, who was among San Francisco's training camp cuts this summer.Shanahan said the team would decide later in the week whether to sign a running back. Another option is promoting Jeff Wilson from the practice squad if Breida can't play Monday at Green Bay.The 49ers will take a two-day break before returning to the practice field Thursday to begin preparing for their prime-time game against the Packers.Figure a point of emphasis will be protecting the ball better, after San Francisco committed five turnovers in Sunday's loss to the previously winless Cardinals. It was the most turnovers for the 49ers since they had five against Seattle on Sept. 15, 2013.But another challenge for Shanahan is keeping his players mentally focused. Many viewed the 49ers as a potential playoff team before the season. Instead, they've lost four of their first five games and suffered a psychological blow when Garoppolo went down."It's different in this day and age where you hear everything," Shanahan said. "It's hard to simplify your world. And with social media, when guys go home, even if guys don't listen to things, their wives do. Their girlfriends do. Their brothers do."When you go through that stuff and don't meet outside expectations, it starts to affect you. And I just try to constantly preach to our guys to be stronger than that [url=http://www.the49ersfootballauthentic.com/kyle-juszczyk-jersey-authentic]http://www.the49ersfootballauthentic.com/kyle-juszczyk-jersey-authentic[/url] , to try to not pay attention to that, because that's not going to help you solve any problems."NOTES: Receiver/punt returner Dante Pettis (left knee) already has been ruled out for a second consecutive game. Several others will be re-evaluated once the team returns to practice Thursday. They include receiver Marquise Goodwin (quad, hamstring), left tackle Joe Staley (knee), center Weston Richburg (knee), tight end George Kittle (knee) and cornerback Jimmie Ward (hamstring).