SAN DIEGO -- The Tampa Bay Buccaneers are a laughing stock no more.

The once woeful Bucs are tied for the NFC South lead after beating the San Diego Chargers, 28-21, on Sunday afternoon.

Tampa Bay is tied with the Atlanta Falcons atop the division after winning its fourth straight game overall and fourth consecutive road contest by outscoring San Diego, 21-7, in the second half.

"I think the Bucs are heading in the right direction,'' said Tampa Bay's Mike Evans.

The second loss in three contests for the Chargers (5-7) dealt a severe blow to their slim playoff hopes. It would be the sixth time in seven seasons the last-place Chargers failed to advance.

"We have four left to play and as you have heard me say in the past, we signed up for all of them,'' Philip Rivers said. "Regardless of the situation and regardless of how tough it is.''

It's not difficult figuring out why the Chargers fell again with Rivers' tossing two second-half interceptions. One of Rivers' picks was returned for a touchdown and the other one came with three minutes remaining in the Tampa Bay end zone.

Keith Tandy made that grab, snatching it away from Dontrelle Inman as Rivers threw his seventh interception in his last three games. Rivers was 15 of 26 for 225 yards, two scores and two second-half interceptions.

"They came out with a formation we'd seen on film," Tandy said, "and actually it was a rookie, Vernon Hargreaves III, who said, 'Hey, watch this route,' and they ran the route he called out, so I just made sure I have good eyes, time it where I get in with the receiver and saw the ball come and tried to make a play.''

Rivers didn't try to make any excuses.

"You give them seven points and you turn it over again down in there, you are probably not going to win,'' he said.

Winston completed 20 of 30 attempts for 280 yards, a touchdown and an interception. He slipped out of numerous situations where the Chargers appeared to have him sacked only to produce positive situations.

"Jameis does a phenomenal job in the pocket of getting out of plays that you think are sacks, minus plays,'' Chargers head coach Mike McCoy said. "We are going to be sick looking at the film and seeing the sacks we should have had. Turn the film on -- that is week in and week out of what he does. He makes the big plays when he gets out of there.''

The Chargers' Melvin Gordon rushed for a game-high 84 yards with a score on 17 carries. He finished eight yards shy of reaching 1,000 yards on the season.

The Bucs forged back ahead with nine minutes to play on Winston's 12-yard touchdown pass to Cameron Brate. Winston then found Evans for a completion and two points for a 28-21 edge.

"Pre-snap, I kind of knew I was going to get the ball,'' Brate said. "I just had to run my route and not rush it too bad and just catch it when Jameis threw it to me. It was a great ball and I was lucky enough to hold on to it.'

Aguayo nailed his second field goal two minutes into the fourth quarter. His 35-yard effort sliced Tampa Bay's deficit to 21-20.

Rivers spotted Tyrell Williams in single coverage late in the third quarter and fired a 40-yard scoring strike to the wide receiver for a 21-17 cushion.

Tampa Bay took its first lead of the game, 17-14, in the third quarter when Lavonte David corralled a deflected Rivers pass and returned it 15 yards for a touchdown.

Rivers threw a quick slant to Williams, but the ball was hit by cornerback Vernon Hargreaves III. It bounced straight to David for the defensive touchdown.

The Bucs pulled to within 14-10 early in the third quarter on Aguayo's 27-yard field goal. For the second straight possession, Tampa Bay was inside the San Diego 11-yard line and both times the Bucs had to settle for field goals.

Tampa Bay was poised to tie the game, advancing to the San Diego 15 with a minute to go in the second quarter. But a sack by Joey Bosa derailed the drive and then Roberto Aguayo misfired on a 31-yard field goal.

Gordon rushed over from 2 yards out, giving the Chargers a 14-7 lead with 10 minutes left in the half. It was Gordon's 10th rushing touchdown of the season, the most by a Charger since Mike Tolbert had 10 in 2010.

Doug Martin plowed in from the 2-yard line to make it 7-7 late in the first quarter. It appeared Martin was stopped in the backfield, but he kept his legs moving to pull the Bucs even.

Casey Hayward jumped a pass directed toward Mike Evans, collecting his NFL-high seventh interception in the first quarter. It gave the Chargers a takeaway in every game this season; they entered the game with an NFL-best 23 takeaways.

But Josh Lambo missed badly on a 53-yard field goal.

The Chargers struck first, capping the game's opening possession with a 45-yard touchdown reception by Inman from Rivers. For Inman, it was his second-longest scoring catch of the season, eclipsed only by his 57-yarder against the Saints.

But the real story is that the Bucs have a share of the divisional lead.

"I've been here for five years and this is the first time we've been playing meaningful football in December, so I can't lie to you it is a great feeling,'' Tandy said. "But we also know we have a lot of work to do so we'll take 24 hours to enjoy it and get back to work."

Added Winston: "It's feels great, but we have not arrived. We cannot stop now.''

NOTES: CB Brandon Flowers remains out with a concussion and was replaced by Craig Mager. ... For the second straight week, RB Ronnie Hillman was a healthy inactive. ... OLB Jerry Attaochu (foot) was placed on IR and NT Ryan Carrethers was elevated from the practice squad. ... WR Cecil Shorts III left the game on a cart in the first quarter with a knee injury. WR Adam Humphries exited the game in the second quarter with concussion symptoms. ... S Keith Tandy filled in for Chris Conte.