HOUSTON -- Monday night's opponent, the Oakland Raiders, may be the toughest one left on the Houston Texans' schedule.

Head coach Bill O'Brien said he thinks Oakland is "playing as one of the best teams in the league," and that the 7-2 Raiders will present a huge challenge, particularly for Houston's defense.

"[Quarterback] Derek Carr is playing very, very well," O'Brien said. "He’s playing good situational football. He can run. He’s got a quick release. He’s accurate. They’ve got some go-to guys in the passing game with Amari Cooper and [Michael] Crabtree, [Seth] Roberts, [Andre] Holmes, the tight end. Like I said [Latavius] Murray, the back, downhill guy, so it’s a tough challenge for our defense."

The Texans' defense has been a strength for Houston so far this season, allowing an average of just 317.4 yards per game, which is the fourth-best in the NFL. Though the run defense has struggled at times this season, the group has done a much better job in the last two games, allowing 58 rushing yards to the Lions in Week 8 and 80 to the Jaguars on Sunday.

Here are six players to watch, courtesy of ESPN Raiders reporter Paul Gutierrez:

OFFENSE

QB Derek Carr: Go ahead, Houston fans, say it without choking: Derek Carr, not David Carr. And yes, the Texans coulda, woulda, shoulda had him with the first pick of the second round of the 2014 NFL draft. Perhaps still gun-shy from selecting big bro David with the No. 1 pick of the 2002 draft, the Texans instead chose UCLA guard Xavier Su’a-Filo and let Carr fall into the Raiders' laps three picks later. Carr, who has started every game since Week 1 of his rookie year, has 17 TD passes and three INTs this season and is edging his way onto the short list for NFL MVP consideration.

OL Denver Kirkland: Who? Exactly. Kirkland, an undrafted rookie from Arkansas who was signed off the Raiders’ practice squad on Sept. 28, has essentially become a 6-foot-4, 335-pound blocking tight end. He’s not about to catch any passes, but Kirkland has been getting plenty of run in place of Lee Smith, who is on injured reserve, in the Raiders' jumbo package. And the Raiders did run for 218 yards against the Denver Broncos last time out behind their gargantuan O-line.

RB Latavius Murray: The Texans have the No. 3-ranked passing defense in the NFL, but only the 26th-ranked rush defense. Murray ran wild against the Broncos’ top-ranked pass defense two weeks ago, rushing for 114 yards on 20 carries with three TDs. So it would only seem natural for the Raiders to want to establish the run game early and often again, right? Keep an eye on change-of-pace mighty-mite backs DeAndre Washington and Jalen Richard, both of whom are 5-foot-8 and excel behind Murray.

DEFENSE

DE/OLB Khalil Mack: The last time the All-Pro defensive end/outside linebacker saw Brock Osweiler, he sacked him five times. That was last December when Osweiler was still with Denver. And after a relatively slow start (one sack in his first five games), Mack has turned it on of late with six sacks in his last four games, including two apiece in his last two games. No doubt Mack will be motivated by the bright lights Monday night’s international showcase in Mexico City will bring.

CB Sean Smith: The veteran cornerback has not played since injuring his left shoulder on the second play of the game at Tampa Bay on Oct. 30. But after practicing the past two weeks (and being inactive), he may be primed to return against Houston. DJ Hayden and TJ Carrie were more than adequate in his stead, and David Amerson has been the Raiders’ best cornerback. But if Smith does return, might he see more of DeAndre Hopkins?

P Marquette King: Yes, he's a special-teamer, but King is sometimes the defense’s best friend because of the way his booming punts can flip the field and pin an opposing offense back deep. King, whose 48.4 average ranks fifth in the NFL, has had 21 punts downed inside the 20-yard line, which is tied for the third-most in the league. He leads, though, in post-punt celebrations -- from mimicking Ray Lewis’ squirrel dance to dabbing to riding an imaginary horse off the field.