As always, Week 1 of the NFL season brought us some tremendous surprises around the fantasy football world. From a rookie quarterback in Tennessee that dominated lackluster competition to a veteran receiver in Green Bay that re-connected with an old friend, here are five of the most-surprising fantasy performances from Sunday's Week 1 NFL action. 

1. Marcus Mariota, Quarterback, Tennessee Titans

In his first regular season NFL start, Mariota threw four touchdowns in just 16 pass attempts. Completing 13 of those passes, Mariota became the fifth quarterback since the start of the 2011 season to finish with a perfect 158.3 rating. In the process, he ended Sunday as the third-best fantasy quarterback. 

There are a couple things to note here. We will provide waiver-wide add advice early this week, but expecting Mariota to come off the street and put up consistent QB1 numbers is foolhardy. Unless you went late with your QB2 option and are not confident in that guy or have a roster spot for a third quarterback, it would be a bit premature to add Mariota in standard 12-team leagues. The reality of the situation here is that Mariota's sample size (16 attempts) could make his Week 1 performance nothing more than an outlier. Even then, it was a tremendous professional debut from the reigning Heisman winner. 

2. Bishop Sankey, Running Back, Tennessee Titans

If you have the Mariota-Sankey stack, congratulations on being foolish. We all get lucky every once in a while. Though, Sankey's Week 1 performance might be more telling as it relates to things to come this season. The Titans' unquestioned starting running back put up 74 yards and a score on just 12 attempts. He added two receptions for a touchdown through the air. All this led to the second-year running back finishing Sunday as the third-best fantasy running back. 

I say that Sankey is the Titans unquestioned starter despite the fact that new acquisition Terrance West put up 13 attempts against the Buccaneers. The primary reason behind this is the fact that West closed out the blowout win with Sankey taking to the bench for some rest. 

3. Alex Smith, Quarterback, Kansas City Chiefs

Smith completed 15-of-20 passes with three touchdowns in the first half of Kansas City's impressive win over the Houston Texans on Sunday. Considering Houston finished in the top third of the NFL against fantasy quarterbacks last season, this is extremely surprising. 

In a sign that Smith's preseason fantasy ADP (162nd overall) was a bit on the low end, his ability to connect with Travis Kelce for six receptions on six targets, including two touchdowns, could signify a turn for the better for the veteran signal caller. Going up against the Denver Broncos on Thursday night, it might be better to hold off one week for a larger sample size before thinking about utilizing Smith as a QB1 or acquiring him when his value is at an all-time high. 

4. James Jones, Wide Receiver, Green Bay Packers

Signed off the street earlier this month to "replace" the injured Jordy Nelson, Jones returned to previous Packers form after a year away from the team. For some reason unknown to mankind, Jones seems to have a great relationship with Packers quarterback Aaron Rodgers — a reality that came to a head on Sunday. Jones caught all four of the passes thrown in his direction for 51 yards and two touchdowns. This was good enough for Jones to finish as Sunday's second-best fantasy receiver. 

Whether Jones' fantasy success has any staying power remains to be seen, but his relationship with Rodgers must be taken into account here. Remember, it was just back in 2012 that Jones finished as the 16th-best fantasy receiver in the NFL. 

5. Austin Seferian-Jenkins, Tight End, Tampa Bay Buccaneers

Here's someone to keep an eye on. We already know that young quarterbacks love to target tight ends as safety valves. That was readily apparent Sunday with star receiver Mike Evans out of action. Rookie quarterback Jameis Winston — making his first NFL start — connected with Seferian-Jenkins on five passes for over 100 yards, including a 41-yard touchdown strike in the fourth quarter. 

The second-year tight end wasn't even considered a mid-tier TE2 in preseason drafts. However, after Sunday's performance, he becomes a rosterable player and someone that possesses the capability of putting up TE1 numbers on a semi-consistent basis. That much was made clear.