Shelvey has fallen out of favour at Swansea in recent weeks and been linked with a move in the January transfer window, with Crystal Palace and Newcastle reportedly keen on the 23-year-old Londoner.
The former Liverpool player did start Swansea's goalless draw at Palace on Monday, but he was substituted early in the second half after an underwhelming performance.
11 Everton 26
12 So'ton 24
13 W Brom 23
14 Chelsea 20
15 Norwich 20
16 B'mouth 20
17 Swansea 19
18 Newcastle 17
19 S'land 12
20 A Villa 8
"There's been questions asked about Jonjo's attitude but in the couple of weeks I've been in charge he's been excellent," Curtis said.
"There's going to be a lot of speculation about Jonjo, he's out of the side at the moment and he's a current England international.
"I guess people are putting two and two together that if he's not in the team he will move in January.
"But I've spoken to Jonjo and he wants to play a part at the club and, unless things change, I expect him to be with us through January.
"He played on Monday and was disappointing, but if you look at his form you've got to look at the entire team as well for most of the season.
"I feel it's a matter of time with Jonjo, potentially he's a great player and the class will always come through at the end."
Only bottom-placed Aston Villa have scored fewer goals than Swansea and Curtis admits that scoring more remains the team's priority in the second half of the season.
France striker Bafetimbi Gomis, who has scored only once in his last 15 appearances and is another who has lost his place in recent weeks, has been linked with a January move to Qatari club Lekhwiya.
Gomis' departure could finance at least one new striker for Swansea in the transfer window but Curtis insists it is a case of adding numbers to the current squad, not diminishing it in any way.
"I hope he (Gomis) will stay," Curtis said.
"You see the speculation in the papers but the chairman certainly hasn't mentioned players going to me.
"We probably need to bolster the squad, I'm not sure if we need to allow people to go out the door the other way."
Curtis takes charge for the fifth time at Manchester United on Saturday having overseen an upturn in form, with the Welsh club now two points above the relegation zone.
Swansea are unbeaten in three, with a win over West Brom and draws against West Ham and Palace, on the back of an unlucky injury-time defeat at Manchester City.
"The fact we've got a couple of results has probably eased the pressure to get somebody in straight away," Curtis said at his press conference ahead of the United game.
"If we'd lost the four games there would be huge pressure to appoint a new manager, but the performances as well as the results have been good.
"I did speak to the chairman (Huw Jenkins) on Tuesday and it's exactly the same position.
"The search for a new manager goes on and we carry on regardless unless the situation changes.
"Things could change, even this week, but it's probably highly unlikely at the moment."