NFL free agency is just ending its first month, but it's fun to study how well offseason planning came together for all 32 teams. The best general managers and coaches know Super Bowl contenders can't be built solely through free agency. Big spenders usually end up the most disappointed.

What I liked about the offseason so far is that franchises realize it will be hard to make significant improvements on offense in this year's draft. This is the second-slowest receiving class in more than a decade. The tight end class is thin. Only one running back is a lock to go in the first round. Defense rules the draft this year.

As I look at some of the best signings, trades and coaching additions made this offseason, offense seems to be main theme. Here are my favorite moves this offseason, ranked 1-10, grouping together similar moves made by teams:

1. The Titans protecting their young QB

The Tennessee Titans made three moves that will help the development of Marcus Mariota. The first was swapping fourth-round picks with the Eagles and acquiring DeMarco Murray to be the featured back. There have been too many times recently that teams draft young quarterbacks and starve them by not getting the right back. Mariota can rely on Murray, and Tennessee will have more of a balanced offense. The second move was signing former Texan Ben Jones at center. A good center can make the right calls and get the correct players blocked. The third move was hiring Russ Grimm as the offensive line coach. Hiring a top offensive line coach can sometimes make more impact than acquiring a free agent starter. We saw that in Pittsburgh with the hiring of Mike Munchak and in Washington with the addition of Bill Callahan.

The Titans are counting on tailback DeMarco Murray to play more like he did in 2014. AP Photo/Michael Ainsworth

2. New England adding more weapons

It's hard to imagine the New England Patriots getting better than the 29.1 points per game they averaged in 2015, but they made six moves on offense that should put them over 30 points. Trading for tight end Martellus Bennett to pair up with Rob Gronkowski was an upgrade over the combo of Gronk and Scott Chandler. It also didn't hurt that they signed tight end Clay Harbor. Chris Hogan and Nate Washington make them better at wide receiver. Jonathan Cooper, acquired in the trade that comes in at No. 3 on my list, should help them at guard. But the best move was getting Dante Scarnecchia back to coach the offensive line, which was a problem last season.

3. The Cardinals-Patriots trade

The trade that sent defensive end Chandler Jones to the Cardinals could end up as a win for both teams. From the Patriots standpoint, they couldn't afford to keep Jones, Dont'a Hightower and Jamie Collins, and sign them all to long-term deals. From the Cardinals standpoint, this was a no-brainer. They acquired Jones, an elite pass-rusher, for a second-round pick and Cooper, whose contract was expiring. The Patriots made a smart adjustment. Sure, they lose Jones, but they can fill some of the void with the signing of Chris Long, and now they have two second-round picks in a draft deep with quality defenders.

4. Philly locking up its own talent

Philadelphia Eagles general manager Howie Roseman has done the best of any front-office executive in investing in home-grown talent. He spent $159 million in contracts on tackle Lane Johnson, tight ends Zach Ertz and Brent Celek and defensive end Vinny Curry. Sometime before training camp, he probably will strike a deal for defensive lineman Fletcher Cox. The Eagles hit it big in the 2012 and 2013 drafts, and that should reflect on the field this year under new coach Doug Pederson.

5. Jacksonville taking a flier on a tackle

Jacksonville Jaguars general manager Dave Caldwell draws praise for the signing of left tackle Kelvin Beachum. Beachum is coming off major knee surgery but should be able to show enough to figure out what to do with Luke Joeckel. The cost was only $4.375 million this year for Beachum. If Beachum looks better than Joeckel, the Jaguars can kick in a four-year, $36 million extension and have the left tackle position locked up until 2020. If Joeckel is the better blocker, the Jaguars can sign him to a long-term deal. If not, they can let him hit free agency knowing they have Beachum at a reasonable price.

6. Atlanta spending for a center

People underestimate what a top center can do for an offensive line. The Atlanta Falcons watched that last season. They struggled. Alex Mack will not only solidify the middle of the Falcons' offensive line, but he will allow the line to get better production out of guard Andy Levitre, a decent acquisition last season. With Jake Matthews continuing to develop at left tackle and Ryan Schraeder becoming one of the better young right tackles, quarterback Matt Ryan should have the best offensive line in front of him since coming into the league in 2008.

New center Alex Mack should lead a much-improved offensive line in Atlanta. AP Photo/David Richard

7. The Vikings adding offensive line help

Minnesota Vikings general manager Rick Spielman had a lot of decisions to make along the offensive line. He helped out the process by signing guard Alex Boone and right tackle Andre Smith. Phil Loadholt has been battling injuries the past couple of years and took a pay cut to stay with the team. He can battle Smith, who signed a one-year deal at $3.5 million. Boone is a Pro Bowl-caliber guard. The next decision is whether to sign left tackle Matt Kalil to a long-term deal.

8. The Raiders spending for defense

Over the past two years, the Oakland Raiders have improved the offense by drafting quarterback Derek Carr and wide receiver Amari Cooper, signing wideout Michael Crabtree and using free agency to build one of the league's best offensive lines. After this offseason, they are well on the way to improving the defense. Sean Smith is a tall corner who can match up in man-to-man against big receivers. Bruce Irvin improves the pass-rush, and re-signing Aldon Smith, who will be available for the second half of the season coming off a year-long suspension, will make them even better. Safety Reggie Nelson is coming off a Pro Bowl season at safety and is the perfect replacement for Charles Woodson. To make matters even better, the Raiders can use a strong defensive draft to get even better.

9. Colts choose a tight end, Saints add one

Indianapolis Colts general manager Ryan Grigson had a tough decision. He had to choose between Coby Fleener and Dwayne Allen. He signed Allen, who is the more complete player. Fleener goes to the New Orleans Saints and should flourish in a Sean Payton offense that was looking for a young, fast tight end who can fill in for what they missed after the Jimmy Graham trade. In the end, both teams ended up with the best tight ends for their franchise.

10. Low-risk deals in Tampa Bay

The Tampa Bay Buccaneers got it right on offense over the past two years by drafting wide receiver Mike Evans, quarterback Jameis Winston, tight end Austin Seferian-Jenkins and others. I loved the low-risk signings of cornerback Brent Grimes and defensive end Robert Ayers. When you look at the Bucs, you know they need to get a cornerback and pass-rushing defensive end in the first two rounds. Grimes and Ayers give them flexibility. They can be one-year fixes if general manager Jason Licht gets the right guys in the first two rounds, or they buy Licht time until he gets the right fits.