New England linebacker Steve Nelson intercepted a Dan Fouts pass at the Patriot goal line with 1:28 to play and preserved a 27-21 defeat of the previously unbeaten San Diego Chargers today.

The Chargers went into the game as the highest-scoring team in the National Football League and they bord witness to their offensive might by charging back from a 20-0 deficit with two quick second-quarter scores.

They rallied again from 27-14 and were driving toward the go-ahead score until Nelson aborted the comeback, leaving Steve Grogan's five-yard pass to tight end Russ Francis early in the fourth quarter to stand as the game-winning strike for New England, now 3-1.

Bob Horn, San Diego linebacker, intercepted a poorly thrown pass and returned it 30 yards to the Patriot 10 to set up the climax with 1:50 to play.

But on third and nine from the nine, Nelson stepped in front of receiver John Jefferson and picked off Fouts' pass. He returned it to the 20, there to lie down, nestling the ball in his arms. The Patriots then ran out the clock.

"If I had 11 blocks I would have scored," jested Nelson, a six-year veteran who plays the left inside linebacker in the Patriots' 34 defense."I was just looking for a place to fall down so I wouldn't fumble the ball.

"We were in a zone defense," Nelson elaborated, "and Jefferson was in the slot to my left. My man was the tight end and he blocked so I was free.

"He (Fouts) telegraphed the pass and I could see right where he was going to throw it. He never saw me," Nelson said.

"Do you think I'd throw an interception right to a guy if I saw him?" an angry Fouts asked.

Grogan, hurt earlier in the last period by an interception, apparently did just that on his interception to Horn.

"I saw him the whole way," Grogan said of Horn. "I just didn't throw the ball right. I was just trying to dink it over his head, but the ball didn't come off right and it went right into his chest. I felt like I had handed the game to him."

The play came on third and 12 from the New England 42 just after the two-minute warning.

Grogan was rolling out to his right and trying to hit an open Francis. Horn was only four yards away and looking Grogan right in in the eyes when Grogan threw.

Horn caught it in the chest and rambled to the 10 before New England tackle Shelby Jordan ran him down with perhaps the biggest tackle the offensive lineman has ever made.

New England went into the game as the No. 2 scoring team in the league and put 20 points up so quickly it looked as if the Chargers didn't know the game had started.

There was a 24-mile-an-hour wind in the Charger faces in the first period and New England took full advantage. The Patriots scored on all three of their first-quarter possessions and the wind aided in each instance.

It stemmed San Diego punter Jeff West with boots of 21, 28 and 30 yards, presenting the Patriots excellent field position on each of their first-quarter possessions -- at the San Diego 34, 47, and 36.

Sam Cunningham scored the first touchdown on a one-yard run, Don Calhoun the second on a 10-yard scamper, and John Smith kicked a 31-yard field goal, for 17 first-quarter New England points.

The home defense kept the Chargers bottled up the entire quarter. In those first 15 minutes, San Diego executed only two plays that gained ground, runs of four yards and one yard by Clarence Williams.

New England increased its lead to 20-0 on a another 31-yard kick by Smith with 6:45 left in the half.

Then the Chargers awoke.

Fouts completed eight straight passes as he drove his team to two touchdowns in the final six minutes of the half to cut the gap to 20-14.

He hit Williams with a six-yard flare, came back with a 33-yard post pattern to the left to Jefferson and followed that with a 19-yard post pattern to the right to Jefferson for a touchdown.

On their next possession, after an 18-yard New England punt into the wind, the Chargers razzle-dazzled to a score. Fouts threw a 15-yard lateral to former Redskin running back Mike Thomas, who threw an 18-yard pass to tight end Bob Klein. Two more Fouts completions led to a one-yard touchdown plunge by Williams.

New England put together its most impressive drive of the day at the end of the third period and the beginning of the fourth as Grogan directed the eventual winning push.

He took the Patriots 64 yards in 10 plays, completing two passes before the five-yard strike to Francis for a 27-14 lead.

Glen Edwards intercepted a Grogan pass at the Patriot 38 with 6:38 left in the game and six plays later, Williams scored again from the one for San Diego.