"Fortunately it's not something that's career-ending--at least I don't think so," Marino said.
Scott Mitchell, Marino's rarely used backup, had his first pass intercepted and returned 97 yards for a touchdown. He rebounded, however, to throw two third-quarter touchdown passes.
Marino has started 145 consecutive games for the Dolphins (4-1) since 1984--not counting the three strike games in 1987--which is by far the longest current streak by an NFL quarterback. Before Sunday, Mitchell had thrown a total of eight passes over the past three seasons.
"Sometimes you do take it for granted," Marino said. "You go out there and play every Sunday and nothing happens. Then all of a sudden when something does, it's a shock."
Marino tore the tendon as he planted his foot to pass late in the first half. He was helped off the field, then returned to the sidelines on crutches in the fourth quarter.
"We are hoping, somehow, some way, that it is not the more serious torn Achilles' injury, which puts him out for the year," Coach Don Shula said. "I don't think that determination can be made yet. It will have to made tomorrow at home."
Before getting hurt, Marino was superb. He completed 14 of 19 passes for 161 yards and one touchdown, a perfectly thrown 13-yarder to Mark Ingram in the right corner of the end zone that gave Marino 298 career touchdown passes. Only Fran Tarkenton has more, with 342.
Mitchell stepped in and started poorly. He immediately threw an interception that Najee Mustafaa returned 97 yards untouched down the right sideline for a 14-10 Cleveland lead. It was the longest interception return in Browns history.
But the left-handed Mitchell was impressive in the third quarter. He completed six of eight passes for 80 yards, including touchdowns of 19 yards to Tony Martin and three yards to Keith Jackson.
The Dolphins' defense clamped down after giving up Bernie Kosar's 14-yard touchdown pass to Michael Jackson on the Browns' first possession. Kosar was replaced by Vinny Testaverde in the fourth quarter.