First-year head coach Corey Mace and his undefeated Saskatchewan Roughriders will meet their toughest matchup yet this week.

Saskatchewan (4-0) visits the B.C. Lions (4-1) on Saturday night in a battle of the West Division’s top teams. The Riders are undefeated through four games for the first time since 2013, while the Lions are 2-0 at BC Place this season and have won four straight.

B.C. quarterback Vernon Adams Jr. is on fire to start the season, leading the CFL with 1,752 passing yards and 11 passing touchdowns. 

The 31-year-old Adams spearheaded last week’s commanding 44-28 victory over the Hamilton Tiger-Cats with 383 passing yards, including 321 to go with four TD passes in the first half alone.

Meanwhile, Riders QB Shea Patterson gets the nod for the second start of his career with starter Trevor Harris on the six-game injured list.

The 27-year-old Patterson replaced Harris last week and threw 192 yards with one TD pass to help Saskatchewan beat the Toronto Argonauts 30-23. Patterson also rushed for 18 yards and a TD.

The Riders picked off Toronto QB Cameron Dukes four times in the win, including two interceptions by Rolan Milligan Jr., to bring their season total to a league-leading nine. Milligan was limited in practice Tuesday, but the Riders will hope to keep the ball from reaching some of B.C.’s star receivers this week.

Alexander Hollins tops the league with 573 receiving yards and Justin McInnis is third with 482. McInnis went for 147 yards against Toronto while Hollins caught 116.

Amid B.C.’s heavy reliance on Adams and passing, tailback William Stanback also leads the CFL with 311 rushing yards.

Riders receiver Shawn Bane Jr. returned to practice this week after missing the Argos game for personal reasons. Bane, who broke out with over 1,104 yards last year, has caught 13 passes for 211 yards to go with three touchdowns in three games.

The Riders are scoring a league-leading 32 points per game heading into the game, while B.C. sits third at 29.4.  The Lions, however, are averaging 423.0 yards of net offence to top the CFL and Saskatchewan is seventh (329.8).

The Riders rank third in opponent net offence (347.8) and the Lions are fifth (353.6).

B.C. has the edge in special teams with kicker Sean Whyte a perfect 14-for-14 this year. Saskatchewan’s Brett Lauther is 9-for-11.

Saskatchewan started the season with two road wins, but their luck may run out. With Adams on a tear and B.C. rolling, the home team gets the edge this week.

Pick: B.C.

Toronto Argonauts versus Montreal Alouettes (Thursday night)

At Montreal, the defending-champion Alouettes (5-0) look to extend their unbeaten streak to 14 games dating back to last season, with their last loss a 23-20 defeat to Toronto on Sept. 15. Toronto (2-2) is looking to bounce back from consecutive losses — including a 30-20 home defeat to Montreal on June 28 — for the first time in almost two years. Chad Kelly-replacement Dukes started the season strong but has struggled passing the ball the last two weeks, going 41-for-66 with zero TDs and five picks. Alouettes kicker David Cote is out while safety Marc-Antoine Dequoy is a game-time decision.

Pick: Montreal.

Calgary Stampeders versus Winnipeg Blue Bombers (Friday night)

At Winnipeg, Blue Bombers (1-4) QB Zach Collaros is expected to start after missing last week with a thorax injury. The two-time outstanding player practiced this week and will aim for his first TD pass this year for the Bombers, who secured their first win of the season 25-16 over Ottawa last week. Calgary (2-2) fumbled an 11-point fourth-quarter lead against Montreal last week. QB Jake Maier managed only 106 yards on 18-for-28 passing with one TD and an interception.

Pick: Winnipeg.

Ottawa Redblacks versus Edmonton Elks (Sunday night)

At Edmonton, the status of Dru Brown is uncertain for Sunday after the Redblacks (2-2) QB entered concussion protocol. The first-year starter left last Friday’s loss to Winnipeg due to a hit to the head from Bombers linebacker Redha Kramdi in the second quarter. The Elks (0-4) are well-rested coming off a bye week and looking for their win after three straight three-point defeats, losing on last-second kicks their previous two games. McLeod Bethel-Thompson and company hope to have better luck at home this week.

Pick: Edmonton. Last week: 3-1.

Overall: 12-8.