PHOENIX -- One day later, D-backs manager Kirk Gibson had a little better handle on what went wrong for starter Daniel Hudson.

Hudson allowed seven runs on 10 hits in lasting just four innings against the Mariners on Tuesday night.

The outing was disappointing, as it came off a fine performance against the Rangers when it seemed he had turned the corner from his struggles.

"They're a very aggressive team," Gibson said of the Mariners. "And if you notice, early he'd get behind in the count and he'd throw his changeup or his secondary stuff, and he wasn't getting strikes, they weren't good enough to get swings. In the end, he was elevating a little bit."

Not being able to get his secondary stuff over especially early was a problem.

"They like to whack the fastball early," Gibson said. "So you have to pitch around that, and he was just unable to execute."

Gibson stands by Upton after boos

PHOENIX -- After his eighth-inning strikeout Tuesday night, D-backs outfielder Justin Upton heard some boos from the home crowd at Chase Field.

"He feels a lot of pressure on him," Arizona manager Kirk Gibson said. "I know the fans were booing yesterday, that was kind of a first. That worries me a little bit."

It's been a frustrating season thus far for Upton, who injured his thumb early in the year and then struggled to find consistency at the plate.

Tuesday, the Mariners elected to intentionally walk hot-hitting Aaron Hill to load the bases for Upton in the fifth inning, and he struck out swinging.

Gibson cringed when he heard the boos, remembering when he heard boos as a player in 1983 from his home crowd at Tiger Stadium.

"First of all, it's not going to help him," Gibson said. "But at the same time, it introduces a new dimension into his growth as a player. He's got to remain determined, and he has to power through that. It's something different. It hurts. There's nobody trying harder than Justin Upton. It will be a good test of his character and his ability to get through this. You're motivated all the time, so if someone boos you, you don't get more motivated. It's something where you have to not let it upset you."

Worth noting

• The D-backs agreed to a four-year extension with the Missoula Osprey to maintain their Rookie League affiliation. The agreement runs through 2016, and continues a relationship that started in 1996 when the club was located in Lethbridge, Mont., before moving to Missoula in 1999.

• Double-A Mobile's Alfredo Marte was named Most Valuable Player of the Southern League All-Star Game. Marte went 2-for-2 with a double and an RBI in the game.

Third baseman Matt Davidson, first baseman Marc Krauss and second baseman David Nick also played in the game.

Left-hander Tyler Skaggs started the game, and allowed one run and struck out one in one inning of work.

• Even with Thursday's off day, the D-backs will stay in rotation, meaning that all the starters will get an extra day of rest this time through the rotation.