UPDATE (April 9, 12:20 PM): The question "What's the earliest the Blazers can clinch the 5 or 6-seed?" has repeatedly come up over the last several hours.
Here's the tl;dr answer: The Blazers can clinch the 6-seed tonight with a win and a Memphis loss against the Golden State. If both those things happen, Portland clinches a 5-seed with a Dallas loss tomorrow night at the Clippers or on Monday at the Jazz. Thus, tomorrow night is the earliest the Blazers can clinch No. 5 in the west.
The Portland Trail Blazers are headed to the playoffs! However, they are still battling the Memphis Grizzlies and Dallas Mavericks for the 5-7 seeds. The Utah Jazz and Houston Rockets, currently in eighth and ninth, respectively, can still sneak into the playoffs, but cannot catch the Blazers.
Here's a rundown of each team's position, and a table of tiebreak scenarios:
Portland Trail Blazers: Control their own destiny. If the Blazers beat the Timberwolves tomorrow night and the Nuggets Wednesday, they will finish in the fifth seed. But, the Blazers do not own the tiebreaker against the Mavericks so a single loss could drop Portland as low as seventh if both Dallas and Memphis win out.
Dallas Mavericks: A major wild card. They're 1.5 games behind the Blazers, but hold the tiebreaker with Portland. They'll finish the season with games at the Clippers, in Utah, and at home against the very-likely-resting Spurs. If they win out, the Blazers will need to win both of their remaining games in order to keep the 5-seed.
Memphis Grizzlies: A tough road ahead. After losing to the Mavs, they no longer control their own fate. They finish the season vs Golden State, at the Clippers, and at Golden State. If they somehow win out, they'll still need a Blazer loss in order to nab the 5-seed.
Utah Jazz: Irrelevant, but... With 40 losses, they can no longer tie the Blazers. However, they're still in a fight with Dallas and Houston. Utah can help the Blazers Monday by beating the Dallas Mavericks. That would give the Blazers a little leeway, or possibly a chance to rest everyone Wednesday night with the 5-seed clinched.
Full standings and tiebreak scenarios follow:
Full playoff tie-breaking procedures can be found here. The most important statistic is head-to-head record. If the two teams finish tied, they will be positioned by the second tiebreaker - conference record.
Updated Tiebreak Scenarios (April 9th):
Head-to-head ties: Dallas holds the head-to-head tiebreaker with the Blazers, so the Blazers need any combination of two Portland wins and Dallas losses to clinch at least the 6-seed. The Blazers do hold the tiebreaker over the Grizzlies by virtue of their better conference record. Thus, the Blazers can stay ahead of the Grizzlies if they win out.
Three-way ties: Three-way ties will be broken by winning percentage in games played among the three teams.
If Portland, Memphis and Dallas finish the season with identical records, Dallas wins the tiebreaker. Portland will finish second in the tiebreak, and therefore take the 6-seed.