Combine: Day 4 observations

INDIANAPOLIS -- Recent NFL drafts have been rich in offensive linemen and tight ends. But from the looks of the first day of workouts at the NFL combine, blockers and tight ends aren't going to be headliners in 2012.

Sure, there will be stars. Matt Kalil of Southern California looks like a great left tackle.David DeCastro of Stanford is one of the best guard prospects in years. As for the tight ends, though, it will be hard to find a sure thing.

Here are five things we learned Saturday at the combine.

1. The Vikings should target Kalil: If Minnesota has a chance to draft Kalil but trades down instead, it should stop its efforts to build a new stadium. At 6-foot-6 and 305 pounds, Kalil is a potential Pro Bowl left tackle. He ran well Saturday, clocking an impressive 4.96 in the 40-yard dash. He's strong enough, lifting a 225-pound weight 30 times. The NFL is in his genes. His brother, Ryan, is a Pro Bowl center for the Carolina Panthers. Seahawks coach Pete Carroll says having an NFL bloodline gets a player noticed a little quicker. Well, Kalil has been noticed and looks like a star.

The Vikings must rebuild portions of their offensive line. Last season, they cut ties with left tackle Bryant McKinnie, who had Pro Bowl talent but inconsistent effort. The Vikings need Kalil to protect the blind side of quarterback Christian Ponder. Plus, the timing is perfect. Steve Hutchinson is in the final year of his contract and will probably retire after the season. Hutchinson, who played with potential Hall of Fame tackle Walter Jones in Seattle, is one of the smartest guards ever and could help a rookie left tackle adjust. With a new stadium on the horizon for the Vikings, Kalil could be the foundation this offense needs on the line.

2. Hall of Fame potential at guard? DeCastro might be the best guard prospect since Hutchinson. For decades, teams shied away from using high draft choices on guards. Guards fill holes between center and tackle, and many personnel people believe they can patch that position. Hutchinson opened eyes when the Seahawks selected him with the 17th pick in the 2001 draft. A seven-time Pro Bowler, the Vikings signed him away from the Seahawks in 2006 for one of the biggest guard contracts in NFL history.

DeCastro didn't run scintillating 40 times (5.43 and 5.47) Saturday, but he looks like a great guard. He's 6-foot-4 7/8 and 316 pounds and bench-pressed the 225-pound weight 34 times. Since 2001, only two other guards were drafted 17th or higher in the first round: Shawn Andrews of the Eagles in 2004 and Mike Iupati of the 49ers in 2010. DeCastro could go higher.

3. Holes exist with some of the other top blockers: While there could be five or six offensive linemen taken in the first round, this isn't a great group. Cordy Glenn of Georgia helped himself by running a 5.15 40, but he's 6-foot-5 and 345 pounds, heavy enough to be more of a right tackle prospect. Mike Adams of Ohio State is intriguing at 6-foot-7 and 323 pounds, but he only pumped a 225-pound weight 19 times, which is considered weak for a top tackle. He has been a tackle since sixth grade, but he needs more strength. Wisconsin's Peter Konz, the best center in the draft, only bench-pressed 225 pounds 15 times. Still, all could go in the first round.

4. Tight ends all over the board: It's hard to say who is the best tight end in the draft. Stanford's Coby Fleener gained an edge even though he didn't work out. Dwayne Allen of Clemson ran 4.89 in the 40, the third-slowest time among the 10 tight ends who ran. Cory Harkey of UCLA hurt his third- and fourth-round grades by running a 5.11. Potential mid-round pick Michael Egnew of Missouri, who is 6-foot-5 and 252 pounds, ran an impressive 4.62 in the 40. The sleeper might be Ladarius Green of Louisiana-Lafayette. He's 6-foot-6, 238 pounds and ran a 4.53. He might have vaulted from the third round into the second round.

5. Could Peyton Manning be the next Joe Montana? Chiefs general manager Scott Pioli and coach Romeo Crennel made it clear they want veteran competition for starting quarterback Matt Cassel. When asked about looking at Manning, if he's cut by the Colts, Crennel said Saturday the Chiefs would be crazy not to consider him. The Arizona Cardinals checked in with similar thoughts earlier in the combine week.
The Chiefs want to bring back veteran Kyle Orton. Signing Manning could kill any competition, but it would be a move similar to the trade the Chiefs made for Joe Montana after he was finished with the San Francisco 49ers. The Miami Dolphins and Washington Redskins seem to have the best chances of signing Manning if he's released, but interested new teams are checking in.

John Clayton, a recipient of the Pro Football Hall of Fame's McCann Award for distinguished reporting, is a senior writer for ESPN.com. Follow Clayton on Twitter