TEMPE, Ariz. (AP) - After a sluggish start, Taylor Kelly made his last home game a fine one.

The Arizona State senior, coming off a subpar performance in an upset loss at Oregon State, threw for four touchdowns and the No. 13 Sun Devils dominated the second half for a 52-31 victory over Washington State on Saturday.

D.J. Foster rushed for three scores and Arizona State converted all five Cougars' turnovers into touchdowns.

Arizona State's Cameron Smith caught six passes for a career-best 131 yards and two touchdowns for the Sun Devils (9-2, 6-2 Pac-12), who can still win the Pac-12 South title, with some help.

Redshirt freshman Luke Falk, in his second start after Connor Halliday went down with a season-ending injury, passed for 601 yards for Washington State (-38, 2-6) but was intercepted four times and fumbled the ball away once. Vince Mayle caught 15 for 265 yards.

Sun Devils defensive end Marcus Hardison had an interception, forced fumble and sack. Arizona State was without standout wide receiver Jaelen Strong, who sustained a concussion last week.

Washington State led 21-7 in the second quarter and 24-21 at the half.

The Sun Devils, also 13th in the College Football Playoff rankings, scored 31 straight points in the second half before the Cougars managed a touchdown with 24 seconds to play.

For Arizona State to earn a second straight trip to the Pac-12 championship game, they must beat rival Arizona in Tucson next week, then have UCLA lose at least one of two remaining games - later Saturday against USC or next week against Stanford.

Arizona State started slowly with six three-and-outs in its first seven possessions but scored two touchdowns in a 41-second span to tie it at 21-21 with 2:31 left in the half. Washington State marched quickly downfield, though, and Quentin Breshears' 27-yard field goal as time expired gave the Cougars a 24-21 halftime lead.

The Sun Devils' hopes for a college playoff spot were dashed a week earlier in a loss at Oregon State, and Taylor had a subpar performance in that game. He's not played to his usual level since returning from foot surgery.

But he launched a perfect 67-yard yard third-period pass to Smith, Taylor's longest completion of the season. It set up Foster's 1-yard touchdown run and the Sun Devils took the lead for good, 28-24.

Hardison hit Falk hard and the young quarterback fumbled. Latu Viliami picked the ball up and rambled 51 yards to the Washington State 18. Foster ran 18 yards for the score on the next play.

The Cougars turned it over again. Salamo Fiso intercepting at the Washington State 38. Seven plays later, Kelly threw five yards to Smith for the touchdown.

Taylor's final touchdown pass came after the Cougars turned it over on downs.