Sophomore QB Drew Lock and the entire Missouri Tigers offense have already been much better in 2016 than they were at any point in 2015.

After throwing four touchdowns and eight interceptions last season, Lock has already thrown for nine touchdowns to go with three picks this season.

He’s completed 55.6 percent of his passes in 2016 and is on pace to throw for more than 4,000 yards. Chase Daniel is the only other Tigers quarterback to accomplish that — he threw for a 4,306 in 2007 and a record 4,335 in 2008 — and Lock would become the first to do so in the SEC.

Lock has undoubtedly taken a big step forward, but the question is how did he progress so much, so quickly?

Here are five of the biggest reasons Lock is on pace to shatter Missouri’s single-season passing record:

1. His receivers are improved: Though J’Mon Moore has dropped several passes and graduate transfer Chris Black from Alabama disappears at times, there’s no question that Mizzou’s receiving unit is better than it was last year.

Adding Black helped and Moore is significantly better than he was last season. Additionally, freshman Johnathon Johnson and sophomore Emanuel Hall have contributed in big ways already this year.

Having players who can make big plays (Moore and Johnson both have 70-plus yard touchdown catches that came off quick screen passes) makes a quarterback look good and feel confident.

Speaking of confidence …

2. He’s more confident: It’s difficult to imagine a season going worse than what Lock went through last season, so having that knowledge has made him more confident this year.

Plus, as a true freshman last year, he was still getting a grip on college life as a whole. Going from high school to playing at Faurot Field and other SEC stadiums is a gigantic leap and it took Lock awhile to adjust.

Now, he’s gone through a year of SEC play and knows what to expect, especially when the Tigers go on the road to places like Knoxville, Gainesville and Tennessee later this season.

3. Josh Heupel’s offense suits him: First-year offensive coordinator Josh Heupel had success at Oklahoma and Utah State and appears to have brought that same success to Mizzou.

Heupel’s play-calling has Lock get rid of the ball quickly, which makes up for an inexperienced offensive line and allows the Tigers to run more plays.

As Lock and Heupel continue to grow more comfortable with each other, the on-field product should improve even more before the season is done.

4. The pace of play doesn’t allow defenses to get set: The Tigers have been running plays at a breakneck speed in 2016, snapping the ball within 10 seconds of when the referees set it in place.

By calling a play and running it immediately, without too much time for reading a defense or calling audibles, Lock is forced to just play football. He’s not overthinking things and it’s helped him grow as a quarterback.

Lock has all the physical skills needed to be a great quarterback. As his mental game comes along, Mizzou’s coaches will allow him more freedom at the line.

For now, though, the Tigers are content to just set him free to make plays.

5. There are more options in the running game: Though graduate transfer Alex Ross is dealing with an injury, the Mizzou rushing attack has more options in 2016.

Ross, Ish Witter (the leading rusher from last season) and freshman Damarea Crockett form a talented trio of running backs.

None of the three has had a 100-yard performance yet, but they’ve all had games with 60-plus rushing yards.

When teams have to respect the running game (which they didn’t have to do last year), it opens up more passing lanes for Lock and the receivers.

The Tigers host Delaware State on Saturday afternoon. The game will kick off at 3 p.m. Central time and can be seen on the SEC Network.