Task: Question Answering
Input (English): Context: Marino finished the game with 29 out of 50 pass completions for 318 yards, 1 touchdown, and 2 interceptions. Clayton was the top receiver of the game, with 6 receptions for 92 yards. Walker returned 4 kickoffs for 93 yards and gained 15 yards on 2 punt returns. Nathan was the Dolphins leading rusher with 18 yards, while also catching 10 passes for 83 yards. Craig had 58 rushing yards, 77 receiving yards, and 3 touchdowns. He was the first player ever to score 3 touchdowns in a Super Bowl, and his 2 touchdown catches also tied a Super Bowl record. Tyler led San Francisco in rushing with 65 yards, and also caught 4 passes for 70 yards. Clark caught 6 passes for 77 yards. Board recorded 2 sacks. McLemore recorded 51 punt return yards, the second most in Super Bowl history. Sports Illustrated called 49ers defensive tackle Gary Johnson (American football) the Super Bowls "unofficial defensive MVP" after he recorded one sack, flushed Marino out of the passing pocket numerous times, and had four unassisted tackles. 
 Question: What "unofficial" title did Sport Illustrated give Gary Johnson?
Output (English): defensive mvp