"Who's going to fill the Net Expected Points (NEP) is a measure of how many points a player produces for his team compared to expectation level. Rushing Success Rate measures the percentage of runs a player had that resulted in a "success", or a NEP greater than zero.

A couple of things jump out in this table. First is just how much better Lewis was on the ground. Not only were his raw numbers better, but he was far more efficient, and the gap in consistency on the ground is massive. Among the 105 backs to record at least 25 carries this season, Lewis' success rate ranks 8th, while White's ranks 103rd.

We also see a bigger distinction in receiving production here, one that doesn't jump out with the raw statistics. On a per-target basis, White holds a significant edge in Reception NEP.

White's 2015 Season

Let's dig in to White' season a little bit more.

He was a complete afterthought in the offense while Lewis was healthy. In games Lewis played this year, White saw the field on only 27 of 342 possible snaps, or just under 8%. Once Lewis went down, White led Patriots' backs, seeing the field on 40% of snaps.

Ranking third in Reception NEP per target among the 58 backs to see at least 25 targets this year, White proved himself to be one of the league's best receiving threats out of the backfield. In fact, he was one of the best we've seen in a while.

If we raise the target threshold to 50, looking at more dedicated receiving backs, White's 0.70 Reception NEP per target is the third best mark in the last decade.

What White doesn't offer, though, is any sort of versatility.

The Patriots have had backs record 50-plus targets in a season 9 times in the last 10 years. White's Rushing NEP per carry ranks dead last among that group, as does his Rushing Success Rate. That -0.17 Rushing NEP per carry ranked 91st among the 105 backs to record at least 20 carries this season.

It's no secret that when White is on the field, the Patriots are going to the air. And if they want to mix things up and run the ball with White, defenses have nothing to worry about. He offers just about nothing in running situations. Which leads us to where Lewis sets himself apart, and becomes so hard to replace.

Lewis' Value

Lewis combines being a solid receiving threat with being an incredible rushing threat, to a degree you don't often see. It went a little bit overlooked, partially because of the "you can't trust a New England running back" narrative, but Lewis was on a truly elite pace.

Just in terms of raw numbers, he was on a 16-game pace for 535 rushing yards, 887 receiving yards and 10 touchdowns. Only three times in the last 10 years has a back managed 500-plus rushing yards and 800-plus receiving yards in the same season.

The advanced numbers are maybe even more impressive.

In the last 10 years, there have been 195 backs to record at least 50 targets and 25 carries in a season. Lewis ranks 19th in this group in Reception NEP per target. White's receiving numbers overshadowed Lewis a bit, but Lewis' production through the air was still very strong.

On the ground he was even better, and in that same group of backs, Lewis ranks sixth in Rushing NEP per carry.

Even if we ignore any receiving production, Lewis ranked third in Rushing NEP per carry among the 100 backs to see at least 25 carries this season, and still leaving out any measure of receiving, Lewis is one of the most effective backs the Patriots have had in recent memory. His 0.18 Rushing NEP is the third best mark posted by a Patriots back in a season with at least 25 carries in the last 10 years.

The Void

The problem isn't just that James White is terrible on the ground, though that doesn't help.

It's that Lewis offers a very rare versatility.

The messiness of New England backfields is up there in notoriety with Mike Shanahan's backfields, and that narrative combined with Lewis' season being cut short overshadowed just how much he was offering.

Lewis completely transcended the "receiving back" role in New England, and it was a rare case of their best receiving back also being their best runner. There aren't many backs in the league that could fill the void left by Lewis, and James White, excellent receiving numbers and all, certainly isn't up to the task.