CHARLOTTE, N.C. (AP) -- Panthers wide receiver Steve Smith is ''highly doubtful'' for Sunday's game against the Atlanta Falcons with a left knee sprain, coach Ron Rivera said Monday.
However, Rivera said he's optimistic Smith will be ready for the playoffs.
The Panthers (11-4) wrapped up a playoff spot Sunday with a 17-13 win over New Orleans. They can clinch the NFC South division title and a first-round bye in the playoffs by beating the Falcons.
Smith had an MRI Monday that revealed a sprained posterior cruciate ligament.
''It was very good news considering the alternative,'' Rivera said. ''Where he sprained it and the lack of severity there was, that was all positive news. It really was. And I'm excited and very happy for Steve.''
Rivera said he spoke with Smith on Monday.
''He told me he doesn't feel very good right now, but you know me,'' Rivera said. ''And we do know Steve. He's very tenacious and he will do everything he can. He will work very, very hard.''
Rivera said it will be difficult playing without Smith because he draws so much attention from defenses.
Carolina's offense struggled on Sunday after Smith went out in the first quarter and failed to convert a third down, going 0 for 9. At one point in the second half the Panthers went three-and-out on four straight possessions and managed a combined 16 yards during that span.
The 34-year-old Smith has 64 receptions for 745 yards and four touchdowns this season.
''Steve is still the big focal point of who we play,'' Rivera said. ''You put the tape on and you still see people matching DBs on him and rolling coverages toward him. That might be something that will be interesting to see what happens - how teams are going to play us. This might be a good thing for us to learn.''
Smith hasn't missed a game since Week 17 of the 2010 season.
Smith injured the knee Sunday running a slant route in the first quarter and was taken to the locker room for observations. He returned midway through the second quarter and ran one route before taking himself out of the game. He was hobbling noticeably as he walked off the field.
Smith told The Associated Press after the game Sunday that team doctors were concerned about his PCL.
''They say it's a nothing injury, but I know my knee doesn't feel like it's nothing,'' Smith said Sunday.
Smith said he felt a ''pop'' when he first injured the knee.
Players were given the day off Monday.
Smith walked around the locker room after the game without much of a limp and did not need crutches. He did not have his knee in a brace either.
Panthers offensive coordinator Mike Shula said losing a player like Smith is ''a big concern.''
''He is such a warrior on game day and a productive player,'' Shula said. ''He presents a lot of problems for the defense and gives you a lot of good looks to help other guys play better. It's time for other guys to step up and be ready. And they're ready. That was no more evident than Sunday.''
Domenik Hixon replaced Smith at the ''X'' receiver spot and caught a game-winning 14-yard touchdown pass from Cam Newton with 23 seconds to help the Panthers clinch their first playoff berth since 2008.
Hixon came into the game with just three receptions all year and no touchdowns.
Rivera said he expects Ted Ginn Jr. will see the majority of reps this week at Smith's spot, but said Hixon and Brandon LaFell could also see action at the ''X'' spot. Shula said the team is likely to activate wide receiver Marvin McNutt as its No. 4 receiver.
Rivera said Newton tweaked his ankle on Sunday, but the third-year quarterback is walking around fine and is expected to practice Tuesday.
Defensive tackle Colin Cole is day to day with a strained calf.