LONDON -- The Detroit Lions face the Atlanta Falcons at Wembley Stadium Sunday as part of the NFL’s International Series. How do the Lions come away with a win and a 6-2 first-half record? Here are four keys.

1. Calvin Johnson: The star wide receiver practiced for the first time this week and said Thursday he could take his decision of whether or not to play all the way to Sunday. Unlike the past two weeks, though, this game might mean a bit more to him. As a huge international soccer fan, playing this game in Wembley Stadium would truly be a once-in-a-lifetime experience for Johnson. And doing it while facing his hometown team, the Atlanta Falcons? That might be too good for him to pass up. If he bases it solely on his health, however, he truly becomes a coin-flip decision. Detroit could use him back in the lineup because the offense has been somewhat stagnant due to his and other injuries to skill-position players.

2. Who plays tight end? The Lions have been down three tight ends for most of the week, and the two who have practiced -- Kellen Davis and Jordan Thompson -- have been with the Lions’ 53-man roster for all of a week. Davis has never even played for Detroit before. If Brandon Pettigrew, Eric Ebron and Joseph Fauria all don’t play, that’s a big spot for a free agent off the street and a practice squad player. Depending on Johnson’s status, this could severely limit Matthew Stafford’s options.

3. Get to Matt Ryan: The veteran Atlanta quarterback has been good at avoiding pressure and sacks this season, even as his offensive line has crumbled around him due to injuries and ineffectiveness. But Ryan hasn’t faced this type of defensive front this season, and while Drew Brees had time on some plays last week, he was pressured enough to force bad decisions, including 10 incompletions and a turnover during the Lions’ rally late in the fourth quarter. If Detroit can do similar things to Ryan, this could be a big game for the Lions’ defensive line.

4. Defend Roddy White and Julio Jones: It’s unlikely the Lions will be able to take away both players, as they have combined for four 100-yard games this season (Jones with three, White with one). White and Jones represent one of the toughest receiving tandems the Lions have faced all season, and covering both while pressuring Ryan will be the key for defensive success. It would not be a surprising strategy to see the Lions not blitz much and have the front four try to create pass pressure and stop the run game, leaving seven players to drop into coverage. This might be a game where Detroit would want to allow more on the run in order to shut down the pass.