When the NFL schedule was announced in April, Green Bay's visit to Tennessee on Sunday figured to be nothing more than a tuneup game for the Packers and an excuse for their fans to turn the Titans' Nissan Stadium into Lambeau Field South.

Well, Green Bay fans could still take over the enemy stadium, but given where the Packers are and how Tennessee has progressed, this looks to be anything but a gimme. In fact, it should be one of the tightest games on the Week 10 card.

At 4-4 after a 31-26 home loss last week to Indianapolis, Green Bay is just a game back of slumping Minnesota in the NFC North. The Titans (4-5) fell 1 1/2 games back of Houston in the AFC South after a 43-35 defeat last week in San Diego.

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Alarms were sounded in Wisconsin after last week's game when players and coach Mike McCarthy took turns bemoaning the team's lack of energy. McCarthy wasted little time Wednesday squelching that issue in regards to this game.

"We'll play with great energy Sunday. That's not a concern of mine," McCarthy said. "It's a road game, so we have that challenge. Our guys will bring it. We're just paying attention to what matters and it's about improvement. We have to learn from last week."

Lesson one might be the idea of getting off to a better start. The Packers coughed up a game-opening 99-yard kickoff return score to Jordan Todman and never seemed to fight back until Indianapolis established a 31-13 fourth quarter lead.

Tennessee had its own issues with getting out of the starting block last week. It fell behind 16-0 early in the second quarter and fought back to take a brief 21-19 lead before San Diego regained the lead for good, aided and abetted by two scores off turnovers by quarterback Marcus Mariota.

Mariota's game last week screamed mixed bag. While he threw for 313 yards and three scores, and added a 14-yard touchdown run, his three turnovers led to 17 Charger points, more than accounting for the difference.

Mariota has made real strides in his second season, but has tossed eight interceptions and lost multiple fumbles, leading to scores that hurt the team's chances of winning.

"It's an ongoing thing for me," he said of working on ball security. "It (stinks) when it doesn't come out to work too well during the course of a game, but that's part of it. That's part of my growing process. It's part of things I can do to get better."

One guy who's noticed Mariota's progress is Green Bay quarterback Aaron Rodgers, who had some of the same issues early in his career before learning to reduce errors.

"From afar, I've appreciated his game for a while now," Rodgers said of Mariota. "He can do it all on the field. He's extremely gifted athletically and he's doing a good job of throwing it efficiently. I'm definitely impressed with the way he's playing."

Rodgers has been dinged by some for not playing up to par, but the former two-time Most Valuable Player is still hitting better than 63 percent of his passes for 2,039 yards with a 20-5 touchdown-interception ratio.

Imagine what Rodgers could do if he had the Titans' running game. Led by DeMarco Murray, the NFL's second-leading rusher at 807 yards, Tennessee is third in the NFL in rushing, enabling Mariota to take advantage of better matchups than he had as a rookie.

But the Titans' strength could run headlong into the Packers' biggest strength. Green Bay leads the NFL in run defense at 75.8 yards per game.

"We feel strongly about running the football and how we run it," Tennessee coach Mike Mularkey said. "It will be a good test for us."

The Titans could get help up front Sunday if left guard Quinton Spain can return from a knee injury suffered on Oct. 23 in a 34-26 loss to Indianapolis. Spain sat out the last two games but was a full participant in practice on Wednesday.

Meanwhile, Packers outside linebacker Clay Matthews didn't practice Wednesday for personal reasons. Matthews missed last week's game with a hamstring injury and has been hampered by nagging ailments throughout the year, affecting the team's ability to mount a pass rush.