This Sunday, the 49ers will kick off the second half of the 2013 season by hosting the very hot Carolina Panthers at Candlestick Park.After a bye week, it's a chance for the 6-2 49ers – on a five-game winning streak – to get some momentum, heading into the next few games that feature such opponents as the Saints, Redskins, Rams and Seahawks.There are many reasons for 49ers fans to be optimistic about their team's chances over the final eight games. For one, the team has figured out a winning formula, with a focus on running the ball offensively and stopping the run on defense. For another, the team is suddenly getting an influx of talent from a long list of players who have been absent. Against Carolina on Sunday, the 49ers will have linebacker Aldon Smith, receiver Mario Manningham, cornerback Eric Wright and defensive tackle Tank Carradine ready to contribute. And, on the horizon, wideout Michael Crabtree will soon return, too.But there is another reason for optimism as well, and that's the status of veteran defensive ends Ray McDonald, 29, and Justin Smith, 34.Both standout players – foundations of the team's 3-4 defensive alignment – appeared to wear...