The Detroit Lions will spend the next two days in Indianapolis practicing against the Colts before the teams open the preseason together on Sunday. Lions coach Jim Caldwell has said joint practices are important evaluation tools. Here are five things I’ll be keeping close tabs on the next two days:

• Kenny G: Third-round pick Kenny Golladay had an impressive first few months with the Lions. Golladay is the biggest receiver on the Lions roster, and his speed and size are evident in one-on-one drills. For the next two days, he’ll get a chance to face unfamiliar cornerbacks in almost-live situations. How he performs could be a prelude of the season to come.

• Vitamin Z: If Golladay has been the most pleasant surprise of camp on the offensive side of the ball, Anthony Zettel owns that distinction on defense. Zettel has taken most of the first-team reps at right end with Ziggy Ansah out. It will be a test for him to go against a solid left tackle in Anthony Castonzo who doesn’t know his moves.

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• Left overs: More than a week into training camp and the Lions still don’t have a clear-cut favorite to start Week 1 at left tackle. Cyrus Kouandjio and Greg Robinson have split first-team reps at the position, and both will be tested this week when they face Colts pass rusher Jabaal Sheard.

• Hilton rewards: The marquee matchup of last year’s joint practices with the Steelers was Darius Slay vs. Antonio Brown. This year, it’s probably Slay vs. Colts receiver T.Y. Hilton. Hilton isn’t on the same level as Brown, who might be the best in the game. But he led the NFL in receiving yards last year and he can fly.

• Luck-ed out: Andrew Luck won’t practice for the Colts as he’s on the PUP list. The Lions won’t have Ansah, and a handful of players in red jerseys – Theo Riddick, Tavon Wilson and Don Carey – likely won’t do much. That means more reps for players like Miles Killebrew, backups who are expected to play key roles this year and can benefit from the experience.

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Contact Dave Birkett: dbirkett@freepress.com. Follow him on Twitter @davebirkett. Download our Lions Xtra app for free on Apple and Android!