It was understood that one of the two remaining undefeated teams in Class 6A boys basketball would fall over the past week with spotless Arvada West and Ralston Valley squaring off last Saturday.

Turns out, nobody is perfect.

Arvada West ended a 12-game losing streak against Jeffco League rival Ralston Valley, which saw a tying 3-point chance hit of the back rim in the waning moments of its 45-42 loss.

The Wildcats moved into the top spot in the CHSAA 6A Selection and Seeding Index — then lost it 72 hours later. On Tuesday, No. 13 Columbine handed Arvada West its first loss of the season, 56-53, behind Cash Boykin’s 29 points and 10 rebounds.

And so, the No. 2 Wildcats (16-1, 6-1 6A Jeffco) and No. 3 Mustangs (16-1, 6-1) are back where they started last weekend, tied atop the league standings with a game ahead (Feb. 21).

More things are inclined to shift in the big-school boys basketball scene this week. Here are a few pivotal matchups across leagues in 6A-4A.

Class 6A

No. 12 Grandview at No. 12 Cherry Creek, Wednesday 7 p.m.

What could be on the line: The 6A/5A Centennial League title.

The Wolves (13-5, 4-1) have one between Wednesday’s possible league title match. The Bruins (13-4, 4-1) have two. None are against teams with winning records.

Grandview had its six-game winning streak snapped on Wednesday in a seven-point loss to No. 21 Overland. Days before, senior Noah Sevy had 22 points in a key league win over Mullen.

Cherry Creek lost to Cherokee Trail by 17 before handing Mullen a 30-point loss on Wednesday.

Windsor at Fossil Ridge, Friday 7:30 p.m.

What could be on the line: Fossil Ridge can take a stranglehold of the 6A/5A/4A Northern League.

6A No. 15 Fossil Ridge (14-5, 8-0) beat 5A No. 9 Windsor (13-5, 6-1) by 32 points last month in a game the Sabercats shot 50% from the field and 44% from 3-point range.

The Wizards have won six straight since then and can get back into the league race with a road win. On Tuesday, they doubled up Greeley West in a 90-45 victory.

Class 5A

Pueblo South at Pueblo Centennial, Thursday 7 p.m.

What could be on the line: Control of the 5A/4A South Central League

The 5A No. 13 Colts (11-5, 4-1) beat 4A No. 19 Centennial (12-5, 3-1) by 15 last month in a game they outrebounded the Bulldogs 40-19.

Of course, a lot can happen over the six days until the two teams meet again. Pueblo East 10-7, 2-2) plays both teams before Thursday with a chance to shift the league standings.

Class 4A/3A

Prospect Ridge Academy at Kent Denver, Tuesday 6:30 p.m.

What could be on the line: Caleb Fay’s mastery of the 4A/3A Metro League.

The now senior has led the 4A No. 2 Sun Devils (15-3, 6-0) to consecutive league titles and has them in position for a three-peat with four league games remaining.

On Tuesday, Fay scored his 2,000th career point in a win over Colorado Academy. He currently has 2,013 points, 635 rebounds and 275 assists at Kent Denver.

The No. 8 Miners (11-4, 2-2) have the kind of weapon to stir things up. Junior Jack Brandt is one of the best players in the league, averaging 26 points and eight rebounds this winter.

PRA is 10 this season when Brandt scores at least 22 points.