Heard's dynamic performance against California brought the Longhorns back from a 21-point deficit in the fourth quarter and saw him set a school record with 527 total yards of offense, surpassing even Vince Young (506) from the 2005 national championship season.
But all of that came because the defense again couldn't get off the field on third down, gave up two fourth-down touchdowns and was routinely pushed off the line of scrimmage.
''An amazing performance by Jerrod,'' coach Charlie Strong said. ''You don't want that to be overshadowed ... (But) we have to get the defense fixed, and we have to get it fixed right away.''
Heard's Young-like performance will be good for nostalgia but was ultimately wiped out by a 45-44 loss. The stirring comeback fell short when senior kicker Nick Rose missed the extra point after Heard's 45-yard touchdown run with 71 seconds left that could have potentially forced overtime.
Strong wouldn't blame the loss on his kicker, noting there were plenty of missed tackles and coverages as Cal rallied with 31 consecutive points.
After three games, Texas (1-2) ranks close to last in the nation in total defense, rush defense and third-down defense, which is particularly troubling as teams continue to push long drives that keep the ball away from Heard.
The Big 12 schedule and the high-flying offenses of Baylor, TCU and Oklahoma loom next. Texas opens conference place Saturday against Oklahoma State. The Cowboys (3-0) scored 69 points against UTSA last week.
''We've got to force turnovers, get off the field and stop the run,'' Texas nose tackle Poona Ford said.
The Longhorns saw what just a few defensive stops can do. Run off the field most of the third quarter against California, the Longhorns forced three punts in the fourth, twice giving the ball to Heard to score.
''We figured out what kind of defense we can be,'' linebacker Peter Jinkens said.
Texas has surrendered up an average of 38 points over the last five games dating to last season, four of them losses. The defense that was the team's strength last season has turned into a liability just as the offense has found some new swagger behind its new quarterback.
Jinkens said the Longhorns have to tap into the hope Heard is promising with his legs and arm.
''When he started making plays, we said now it's our turn,'' Jinkens said.