By Matt Kelley (@Fantasy_Mansion)

Special to Yahoo Sports

The Golden Rule of Fantasy Football: Opportunity Is King.

Just ask Tim Hightower, and every player ever tethered to Drew Brees. Meanwhile, the best fantasy gamers chase touches and targets, because last season’s efficiency can be misleading.

Avoid Chasing Efficient Outliers

Look at Atlanta’s offense last season. Matt Ryan posted one of the highest Adjusted Yards Per Attempt (AY/A) in NFL history playing one helpless secondary after another.

Top-10 Adjusted Yards/Attempt Seasons Sick Luckman (1943) 10.96 Nick Foles (2013) 10.54 Aaron Rodgers (2011) 10.50 Otto Graham (1947) 10.25 Peyton Manning (2004) 10.24 Matt Ryan (2016) 10.09 Milt Plum (1960) 9.97 Otto Graham (1953) 9.83 Johnny Unitas (1964) 9.62 Bart Starr (1966) 9.57

Operating in that hyper-efficient offense, Tevin Coleman was one of the most efficient running backs featuring a +50.9 Production Premium (No. 1 among NFL running backs) on PlayerProfiler.com, and Taylor Gabriel was one of the most efficient wide receivers, evidenced by a +54.9 Production Premium (No. 1 among NFL wide receivers) in 2016. As cogs in an unlikely offensive juggernaut, neither Coleman, nor Gabriel, can be expected to exceed their expected fantasy points by such a wide margin again in 2017.

In the case of Coleman and Gabriel, last season’s efficiency was a counterintuitive red flag, suggesting the players will likely be overvalued in 2017 fantasy drafts. Coleman and Gabriel exemplify why, in most cases, fantasy footballers should discount previous year efficiency rather than chase it.

When Does Efficiency Matter?

While efficiency is often a red herring metric in seasonal formats, it can be a powerful tool for evaluating particular players in a redraft context. Past efficiency really matters when external forces radically change. Efficiency matters most specifically when a player’s situation shifts, his role changes, or the team upgrades his supporting cast.

Which fantasy-relevant players fit this description?

Buy Ty Montgomery

Montgomery was the most efficient running back per touch in the NFL last season. He finished the season Top-3 in the following key metrics: Yards Created Per Touch, Breakaway Runs Per Touch, and Juke Rate (Evaded Tackles Per Touch) on PlayerProfiler.com.

Ty Montgomery’s Exceptional 2016 Efficiency (via PlayerProfiler.com) Yards Created Per Touch 2.8 (Ranked #1 among NFL RBs) Breakaway Run Rate 9.1 (#2) Juke Rate 34.7% (#3)

Amazingly, last year was Montgomery’s first season playing running back full time. Looking back to his college career, when Montgomery carried the ball at Stanford, he posted a mind-bending 8.6 yards per carry, and then displayed excellent athleticism at the NFL Scouting Combine. Specifically, Montgomery’s 129.4 Burst Score reached the 90th percentile.

Ty Montgomery Advanced Stats & Metrics on PlayerProfiler.com. More

Spin it forward to 2017. Going into his second year as full-time running back, Montgomery added muscle mass and worked extensively with explosion and footwork gurus throughout the offseason. While Montgomery refined his running skills, Green Bay purged their running back corps this offseason. The Packers then waited until the fourth round to replenish their backfield.

Montgomery’s 2016 efficiency metrics indicate that he is poised to take over as the Packers’ bell cow back. With an all-around skill set in one of the NFL’s most efficient offenses, Montgomery looks like David Johnson-lite headed into this season.

Draft Adam Thielen

Thielen was the signature dark horse fantasy producer of 2016. Thielen’s 44.6 PPR points in week 16 ranked No. 1 among receivers, meaning savvy fantasy gamers who started Thielen in their fantasy Super Bowl likely won the championship. Looking back at Thielen’s breakout season, for the first time in years, a receiver ranked in the top-10 across every key efficiency metric on PlayerProfiler.com.

Adam Thielen’s Excellent 2016 Efficiency (via PlayerProfiler.com) Yards Per Target 10.5 (#4 among NFL wide receivers) Catch Rate 75.0% (#5) Contested Catch Conversion 83.3% (#7) Production Premium +30.0 (#3) Target Premium +34.8% (#4)

While hyper-efficiency rarely carries over from year to year, a tailwind of situational forces will propel Thielen this season.

Sam Bradford and Thielen were afforded a full training camp to build trust and rapport. Last season, the Eagles traded Bradford to the Vikings just in time to lead Minnesota’s offense against the NFL’s most difficult pass rush defenses while being “protected” by the league’s most injured offensive line. Think about that.

Fortunately, the Vikings face the NFC South and AFC North this season. Hello Cleveland! Hello New Orleans in Week 1! If Bradford can set the NFL record with a 71.6-percent completion percentage against impossibly wicked pass rushes, imagine the fantasy points that he and Thielen will post against the Lions, Bengals, and Bears… Oh my.